PORT ST. LUCIE — To understand the power of Shintaro Fujinami, turn to DJ Stewart.
The Mets outfielder/DH learned last season that 103 mph heat hurts even when it doesn’t drill you.
Stewart saw the best of Fujinami on Aug. 6, when the then-Orioles righty struck him out on three pitches. All were triple-digits heat, the final fastball at the top of the zone registering 102.6 mph.
Stewart swung three times and left with not just a K but a wrist issue.
“I had some inflammation after that at-bat,” said Stewart, who talked with the Mets about the source of the injury, and they all came to the same conclusion: perhaps he swung too hard, perhaps he gripped the bat too tight, but it happened against Fujinami. “That’s the only thing that we can think of.”
Among the most electric — and among the most wild — pitchers in baseball, Fujinami is vying for a bullpen job with the Mets after an offseason signing that Stewart said he celebrated.
It is now opposing hitters and not Stewart who have to beware of the 6-foot-6, 180-pound flamethrower.
Fujinami averaged 98.4 mph with his fastball in his rookie MLB season last year but also pitched to a 7.18 ERA.
The Japanese righty could not find the strike zone and did not stick as a starter with the A’s, who sent him to the Orioles in July.
Fujinami was better out of Baltimore’s bullpen and often untouchable, but his control issues lingered.
Among pitchers who logged at least 60 innings last season, Fujinami’s 5.13 walks per nine innings were the ninth-most in baseball. In just 79 innings, Fujinami drilled seven batters.
Fujinami is definitely a project, but one whose stuff tantalizes as much as anyone’s in baseball.
Back on Aug. 6, Fujinami needed six total pitches to sit down Pete Alonso and Stewart before Omar Narvaez came to bat.
“Three pitches to me, too,” Narvaez remembered with a smile, somewhat proud that he then popped up an 0-2, 102 mph dart. “I was cheating on the fastball.”
Narvaez saw the other major weapon from Fujinami, a 94 mph splitter that looks just like his fastball until it disappears under the zone.
Narvaez caught a bullpen session from Fujinami in camp and came away impressed with a splitter that moves more than he remembered.
“He throws gas,” Narvaez said. “We just got to get him to throw strikes.”
Fujinami received his first test Thursday night, when he made his Grapefruit League debut before his best fastball did.
Fujinami threw 10 pitches — plenty of splitters, a cutter, a sweeper and a fastball that touched 94.6 mph — against the Nationals and got two ground outs and a fly out in a clean seventh inning.
“The fact that he was attacking the strike zone, it was good to see,” manager Carlos Mendoza said after the 3-1 win at Clover Park.
Fujinami said he felt “relieved” upon finally beginning his buildup. The 29-year-old is a bit behind after a visa and personal issue delayed his arrival until Saturday.
The Mets believe he still has plenty of time to be ready for the start of the season.
“If I tried I could have thrown harder than today’s velocity,” Fujinami said through interpreter Issei Kamada, but the 29-year-old wants to ease in.
Despite the major league pact, Fujinami is not a lock for the Opening Day roster.
He still can be optioned to the minor leagues, and the Mets could ask him to prove he can consistently throw strikes before calling him up.
His location improved as last season wore on, but he still walked 4.55 batters per nine innings with Baltimore.
“Toward the end of last year I was feeling very good. I’m just going to work hard and get better every day,” Fujinami said upon arriving in Mets camp. “The biggest thing is I attacked the zone more [in the second half].”
There are about a dozen relievers in Mets camp vying for two spots, and several — including Phil Bickford, Yohan Ramirez and Sean Reid-Foley — could be lost on waivers if they do not make the club, giving them a tiebreaker.
It is possible the Mets guaranteed $3.35 million to a pitcher who will begin the season at Triple-A Syracuse.
If the organization’s pitching minds can eventually help Fujinami figure out how to throw strikes, the money would be well-spent.
“It’s special. You don’t see too many people that throw that hard,” Stewart, who was out of the lineup for six days after that painful strikeout, said of Fujinami. “It was definitely riding up at 103.”