How can he have "all the arm talent in the world" but not be accurate? It seems to me that "arm talent," as you're using it means arm strength and nothing more.

SOTW - such a good question - am not a QB expert so there's better folks am sure that can answer that question; however, I'll relate the three keys you can use as a primer that I was given to focus on a QBs arm talent, and a fourth that we didn't even think about much back then and then a few examples of classic QB arm talent and modern Broncos arm talent:

• Arm strength - the obvious one - without the proper arm strength to play at whatever level playing at then won't be able to make the play without the defense being a major factor - doesn't matter if lining up for a YMCA flag football team tryout or the rookie QB for the Broncos
  
• Accuracy - while we all know that the accuracy is a factor in completing passes the reality is that most people have NO concept of where QBs throw to - most often they throw to spots and work on that accuracy to put it there continuously, the receiver has to adapt his route normally to be at that spot not the other way around unless of course an extended or we called a "broken play"
  
• Catchability - not the timing of getting the ball out as that's more a drill that is more about the play than the QB in this case, and that's another nightmare as our rule of thumb was a 3 count now it's 2.5 seconds - the timing of the throw has to match to it being catchable. Compare it to baseball - if a pitcher only has one pitch, say a fastball then what happens if needs to throw a curve or off-speed pitch. If the receivers not in position to receive a ball hot, then it's not going to be a completion - there needs to be the ability to take something off of it at times too.
  

Here's another arm talent factor that am adding as it wasn't really a factor when I played or started to evaluate players:

• Off platform - back in our day you were taught to find that platform, get square and throw the ball over the top - who has time for that anymore - it ain't happening. You've got to be able to adjust your arm angles and make throws, even adjust your core and body to get a ball out - to be fair RW as a former infielder in baseball had that ability - there's a few things RW does really well - moon ball and off platform throws are two of them.
  

Now let's look at a few older and now recent examples relative to the Broncos for arm talent using these factors to equate whom I see as the top dawgs in arm talent. Am going to use first three classic NFL QBs for this exercise - my man John Elway, the GOAT Tom Brady and Mr. Pure Passer Dan Marino (Dan Fouts was the original Dan Marino so what applies for Marino applies for Fouts too):

First let's review John Elway:

• Arm Strength - the US Army is still trying to steal a patent to that arm for their shoulder launched rockets.
  
• Accuracy - for the most part extremely accurate - could get a bit hairy once in a while but generally spot on the money
  
• Catchability - every QB no matter who generally has a flaw in their arm talent that needs improved - when Elway came into the NFL receivers were not so much a fan - everything was hot - I remember a game maybe preseason and a flare pass Elway guns it to the RB and it hits his chest pads and bounces up and out into the stands easily 15-20 yards - the RB stared at Elway like Dude - I'm right here. Somewhere about year five or so it clicked, and Elway started mixing up his throws far better and towards the end he was able to throw a variety of passes
  
• Off Platform - maybe the best rollout QB off platform thrower in his era. They didn't do the kind of weird angle throws that Mahomes has brought into vogue now, so cannot judge that but Elway didn't have to have a clean pocket to get the ball out.
  

Next up Tom Brady:

• Arm Strength - coming into the NFL was actually average to above average - yet he knew he had to get that out there for deeps and worked like a mad man on pliability in particular and his core - it paid off - he's or was very capable of bombing it 60 yards or more even at the end in TB.
  
• Accuracy - other than Joe Montana and Dan Marino maybe the most accurate thrower with the least talented receivers, other than Moss of course - he lifted all boats with his accuracy.
  
• Catchability - super catchable - his knack for putting it into the receivers' hands was off the charts - QBs should study film at how Brady used the ball as almost a handoff to receivers was so catchable.
  
• Off Platform - well like said everybody has improvements they can make - Brady never got much further than being able to move around a bit in the pocket - strictly a pocket passer. Like Marino he used that quick release to defeat the inability to make throws off platform as got rid of the grenade without holding onto it.
  

Finally, Dan Marino:

• Arm Strength - that cock back to his ear hole and still rifling it 20 - 30 yards on a clothesline to his receivers - amazing. Then if he wanted to bomb it - oh boy - 60 yards were nothing for Marino. Elway had more the baseball throwing motion of an overhand pitcher or outfielder. Marino like Fouts generally threw darts - and they were such big strong guys they could get a wrist flick from their ear 30 yards down field.
  
• Accuracy - seriously do you have to ask - Marino was the epitome of hitting the receiver on his break, on his spot and in his route - he made Smurfs into NFL All-Pro receivers with his accuracy. Paul Warfield made Bob Griese - Dan Marino made Duper & Clayton.
  
• Catchability - frozen rope or a rainbow - Marino could throw them all with touch - or heat. Marino could make any throw at any time on the field and the receivers knew it too and were always ready as Dan had one favorite receiver - the guy open.
  
• Off Platform - a race 40 yards between Marino & Fouts would have been timed in minutes not seconds - total statues that survived by the quick release - that ball came out in 2 or 2.5 seconds even back then, otherwise; they knew what they were having for lunch. They didn't take an inordinate number of sacks not due to off platform throws just due to quick releases.
  

Rating this group actually found Dan Marino to have better arm talent than Elway the first three to five years they were both in the league. Once Elway started throwing a bit of junk as they'd say in baseball then I think he equaled Marino. Overall Elways off platform or off schedule ability makes him my overall #1 QB and Marino #2. The GOAT is the GOAT and along with his mentor Montana sorta beyond the QB rating system though was indifferent towards Montana as a 49'er - always respected the player. Neither Brady or Montana needs my rating of Elway or Marino ahead of them as NFL QBs to hold their SB rings for them - they're both doing fine.

Rating the Broncos QBs arm talent:

First up - the Zachster:

• Arm strength - he's got that big gun - he can throw 60 yards with ease and it can come in hot - real hot. Other than Justin Fields and maybe Trevor Lawrence he's got the biggest gun in his draft class.
  
• Accuracy - not really sure to be fair. You wonder with the Zachster what he's seeing - he might be dead spot-on accurate with his reads or that may just be the majority of his problem not getting his reads at all correct. Haven't seen enough to define that though am leaning towards that between the earholes as the problem.
  
• Catchability - many NFL DBs rate the Zachsters passes and throws as some of the easiest to catch in the NFL at this point in his career.
  
• Off Platform - ah the blessing and the curse, the Zachster can move, he can throw on the move - he can throw off platform on the move - unfortunately they often are not to a receiver on his team.
  

Next up - Jarrett Stidham:

• Arm strength - totally NFL ready, can get it there and beat the DBs under majority of circumstances. Not sure if he's better or about same as Nix, close enough a head you win - tails you lose deal for either one really - they're both adequate to a bit above average for NFL arms.
  
• Accuracy - am okay with his placement - yet he's not had enough starts to fully judge that and have seen a few balls where questioned what he was seeing more than the physical yet a potential concern if was a QB1 as a starter.
  
• Catchability - drops in like a baby in a receiver's hands - he really has good spin and trajectory to put the ball in an easy place for receivers to handle it - one of his strong suits IMO.
  
• Off Platform - doesn't look to be Stidham's strong suit - at Auburn he got baby sealed way too much and still see that pattern sometimes showing up. Like RW he can sometimes hold the grenade too long - unlike RW he really has nowhere to go and eats the pigskin or throws it away if lucky.
  

Finally - Bo Nix:

• Arm strength - yet TBD - anyone projecting how a rookie is going to use his arm strength in NFL games is playing tricks with their mind. We just don't know - he looks capable and when given a decent route runner do like the intermediate throw, he puts it spot on over the shoulder 20 yards down field and that's why Kordell Stewart had to be like Tayson Hill a part time QB in the NFL as could not make that throw to save his life. Heck Dak Prescott in just last couple of years is able to make it as requires strength and touch.
  
• Accuracy - generally very good as long as on time & can see it - he does though at times miss the short throws as no YAC as receivers have to dig out the ball, or deeps have to stop and turn around for the ball. That may or may not be an area of concern for Payton as have NO idea how he's doing in the drills other than what's been shown on clips.
  
• Catchability - if it's at the right place & right time then very catchable. Good spin, well timed most often for the speed to meet the need to make a completion. I think this could be one of his strong suits as long as ball placement is accurate.
  
• Off Platform - this dude is an athlete - Mahomes has nothing on Nix, have seen him throw sliding onto his knees sidearm to make completions. He's the epitome of the modern day athletic QB that has to find a lane or window to throw through - very adept at off platform throws. My fave is his rolling right jump pass - he crushes it up to 30 yards downfield no problem.
  

Overall, the arm talent advantage is with the Zachster. IF he could get the mind and arm working together. That said Nix looks way more dangerous as a QB1 than Stidham or Zachster due to ability to run, throw off platform and not a liability with arm strength. Nix's accuracy will have to be thoroughly evaluated in TC - preseason and then as the starter to see if by the bye week or NLT end of season can make a real assessment on Nix arm talent and viability as a QB1 going forward.