Mets president of baseball operations David Stearns spent this past offseason constructing his rotation for depth over flash: He signed Sean Manaea, Frankie Montas, Clay Holmes and Griffin Canning to relatively short contracts, chose to retain Paul Blackburn instead of non-tendering him and converted Holmes from reliever to starter.

Friday afternoon showed the value of that philosophy, and the Mets’ 7-5 loss to the Rays at Citi Field on Friday evening showed its potential pitfall.

Kodai Senga, who leads the majors with a 1.47 ERA, landed on the 15-day injured list with a low-grade hamstring strain, the team announced after the game. He’ll be shut down for about two weeks and reevaluated in what manager Carlos Mendoza classified as relatively good news.

Blackburn, who is slated to take Senga’s spot in the rotation on Wednesday, allowed four runs in relief as the Rays stormed back from a four-run, sixth-inning deficit.

Later in the frame, it was Max Kranick, recalled from Triple-A Syracuse on Friday to take Senga’s place on the roster, who gave up a go-ahead two-run homer by Danny Jansen. The Rays entered the sixth down 5-1 and left it up 7-5.

“It’s been tough” coming out of the bullpen, said Blackburn, who was told he was going to get into Friday’s game to keep his throwing program on schedule for his upcoming start. “I left some pitches up, I left some pitches over the middle and they didn’t miss them.”

The Mets threatened comebacks in the seventh, eighth and ninth. In the final inning, Pete Fairbanks allowed a one-out single by Jeff McNeil and walked Starling Marte. Brett Baty hit into a forceout at second and Ronny Mauricio struck out looking on three straight sliders.

Every run the Mets scored was unearned, and their winning streak was snapped at six games despite three Rays errors.

All that erased a strong start by Holmes, who allowed one run and three hits in five innings, striking out three and walking two. He threw only 79 pitches after feeling some fatigue from his last start in Colorado, which isn’t uncommon because of the altitude. The plan was to limit him to 85 pitches, Mendoza said.

The Rays’ Jonathan Aranda hit a leadoff homer in the fourth, but the Mets got two back in the bottom of the inning.

With the bases loaded, Marte hit a ball that looked as if it were guided by Angels in the (in)field. The comebacker smacked starter Taj Bradley in the ankle and deflected toward Pete Alonso, who dodged it but obscured shortstop Jose Caballero’s view enough for it to skitter off his glove and drive in Juan Soto with the tying run.

Marte’s two-out, two-run single in the fifth gave the Mets a 5-1 lead, but Blackburn entered in the sixth, and so began a six-run implosion.

He allowed three straight singles to load the bases with none out and, one batter later, Jake Mangum flared a two-run single to draw the Rays within 5-3. Kranick allowed a run-scoring groundout by Caballero and Kameron Misner’s RBI single tied it.

Jansen then launched an 89.5-mph slider that crossed through the heart of the plate 389 feet to put the Rays ahead 7-5.

Though the Mets entered the day with an MLB-best 2.80 ERA, that sixth inning aptly illustrated the precariousness of their situation. Senga’s injury, which he suffered while reaching for a ball over his head while covering first base Thursday, means he joins Montas (lat) and Manaea (oblique) on the IL.

“You hate to see it, especially [when] we’re talking about a guy like Senga with the way he’s been throwing the baseball,” Mendoza said. “But we also feel good with the options that we’ve got currently in place. They’ve been doing it the whole year, and they’ll continue to do so. It’s part of it, like I said, but losing Senga, obviously, is a tough one.”

Montas, who’s been struggling in his rehab assignments, started for Triple-A Syracuse and had another rough outing, allowing eight earned runs and seven hits in 1 2⁄3 innings. He’ll have at least two more starts in the minors, Stearns said. Manaea, who began his rehab assignment on June 6, won’t return until at least late June or early July. Still, the Mets currently have two healthy starters — Holmes and David Peterson — with sub-3.00 ERAs.

“I’m very happy with how the group that we have has pitched,” Stearns said. “I’m excited that we continue to get healthier and get guys like Frankie and ultimately Sean back in the rotation. I think that will make us stronger and ultimately deeper.”

Added Mendoza: “We’ve been talking about our depth and here we are again getting tested . . . Injuries are a part of this game. Every team will go through it, but I feel like we’re equipped to handle it.”

Outfielder Jose Siri (broken tibia) suffered a setback after medical imaging showed that the bone had not healed as the Mets had hoped. He’ll be shut down from baseball activities for a few weeks and then be re-imaged before restarting his progression, Stearns said . . .  Lefthander Brooks Raley (Tommy John surgery) is throwing live bullpen sessions, and if all goes well, he could commence a rehab assignment sometime next week. “This is not a short rehab assignment,” Stearns said. “We’ve got to go through a full spring training ramp [up] to make sure he’s ready to go .  You might be looking at the full 30 days there.” . . .  Stearns also said Jesse Winker (oblique) is progressing but still is multiple weeks away from a rehab assignment.