PHILADELPHIA -- Before Monday, the Mets had seen only flashes of Edwin Díaz’s brilliance. The end results for Diaz had been just fine, albeit with a fair bit of shakiness en route.

Monday, Mets manager Mickey Callaway hesitated to use his most potent bullpen weapon for over an hour, warming Diaz multiple times in the Citizens Bank Park bullpen but never bringing him into the game. When he finally unleashed Diaz in the 11th inning of the Mets’ 7-6 win over the Phillies, Callaway’s closer delivered the type of vintage performance the Mets had yet to enjoy: three consecutive strikeouts on 11 total pitches, the last of them clocking in at 99 mph.

That dominance, along with Rhys Hoskins’ game-changing error in the top of the inning, was not enough for Callaway to escape nearly 11 minutes of postgame questioning about his bullpen usage and other tactics. But it was enough for the Mets -- and their management -- to breathe a collective sigh of relief after what Callaway called a “really important” divisional game.

“It’s going to be a battle -- we’ve seen it already this year with every division opponent we’ve played,” Callaway said. “It’s going to be a battle and you’ve got to play clean games. We got away with some stuff.”

In sum, the Mets got away with Noah Syndergaard giving away two leads; with their staff as a whole walking eight batters; with their offense going hitless from the seventh through ninth innings; with Dominic Smith growing so frustrated at one point that he slammed his helmet to the ground, snapping off the ear flap and earning a reprimand from home-plate umpire Lance Barksdale; and with other such transgressions along a four-hour, 39-minute tangle of a game.

The sequence they seemed unlikely to survive occurred in the eighth inning, when Callaway made a series of old-fashioned bullpen decisions that he later described as his new philosophy -- a clear break from the blueprint he drew after taking the job, back then preaching the importance of using his best relievers in the highest-leverage situations possible.

Now, this is the new normal: With a one-run lead and left-handed Phillies slugger Odubel Herrera leading off, Callaway eschewed lefty Justin Wilson in favor of Jeurys Familia -- his “eighth-inning guy.” Familia allowed a single to Herrera, then issued a walk. He would have ceded another single had Jeff McNeil not made a highlight-reel dive to start a 5-4-3 double play, saying afterward that “he just happened to smoke it at me and it happened to find my glove.”

Given that reprieve, Familia doubled down on his ineffectiveness, walking the next two batters to load the bases.

Diaz, the Mets’ best reliever, had not pitched since Thursday. But Mets officials decided before the season never to use him for more than three outs, according to Callaway, despite Diaz’s willingness to do so. So in the tightest of spots, Callaway turned instead to Robert Gsellman, who forced in the tying run with a four-pitch walk.

Gsellman returned to pitch a clean ninth, Luis Avilan survived a shaky 10th, and had the Mets not taken the lead on Hoskins’ error in the 11th, Callaway would have asked Drew Gagnon -- a career Minor Leaguer called up before the game “in case the worst happens” -- to take the mound instead of Diaz. Never, Callaway said, will his closer pitch in a tie game on the road.

As it was, fortune favored the Mets. Juan Lagares led off the 11th with an infield hit and moved into scoring position on a walk, then Michael Conforto grounded a ball that skipped off Hoskins’ glove. Lagares scored from second and, given a one-run lead, Diaz finally entered to mow down the Phillies.

“I would do whatever he wanted,” Diaz said afterward, when asked if he would have preferred to pitch earlier. “I would be ready every time when they needed me. If they want to pitch me three or more outs, I’ll be ready. If they want to pitch me one inning, I’ll be ready.”

In a bustling postgame clubhouse, general manager Brodie Van Wagenen described the Mets’ bullpen strategies in less static terms than Callaway, saying the team “can always deviate from any rule.” Callaway indicated the Mets won’t do so with Diaz until “we get to the playoffs.”

Perhaps at 10-6 and with a half-game lead in the National League East, the Mets are heading there. To continue trending in that direction, they’ll need Diaz at his best -- whether for three outs, four or however many the Mets choose.

“They’ve got their opinions,” Diaz said. “I have to be ready when they need me.”