MIAMI -- Buck Showalter doesn’t sleep much anyway, or at least that’s what he’s fond of saying. When Showalter lay awake in bed before Opening Day, it wasn’t because he knew Mets co-ace Justin Verlander was headed to the injured list. At that point, Showalter hadn’t yet heard the news.

Even if Showalter had been aware of Verlander’s injury, he’s not the type to spend time fretting. Showalter prefers action. When the Mets lost Edwin Díaz to a torn patellar tendon in his right knee during the World Baseball Classic, for example, Showalter offered a few laments before moving onto what he could control: the complexion of his bullpen minus the best reliever in baseball.

New York’s 5-3 Opening Day win over the Marlins offered some hints as to how that might look over the course of the season. Drew Smith, Brooks Raley and David Robertson retired nine consecutive batters in the seventh through the ninth innings on Thursday, with Robertson recording the save in his Mets debut at loanDepot park.

“Edwin, as everybody knows, he’s not replaceable,” Raley said. “I think we all recognize that and know how great he is. As a group, we’ve come together and know that we’ll each be relied on individually to do different things.”

For this unit, the task began in the seventh. Staked to a three-run lead in the middle innings, Max Scherzer gave it back on a pair of doubles and a two-run homer by Garrett Cooper. But the disappointment did not linger for the Mets, as Brandon Nimmo hit a go-ahead, two-run double in the top of the next inning.

With Scherzer’s pitch count creeping over 90, Showalter handed things over to a bullpen that had endured the brunt of the team’s Spring Training misfortune. Of the seven players the Mets placed on the injured list before Opening Day, six were pitchers. Half of those were relievers who seemed primed to play significant early-season roles: Sam Coonrod, Bryce Montes de Oca and, of course, Díaz.

But the Mets built their roster this offseason with an eye toward pitching depth in both their rotation and bullpen. They arrived at camp boasting what general manager Billy Eppler classified as five high-leverage relievers -- a group including Díaz, Robertson, Raley, Smith and Adam Ottavino. All but Díaz made it to Opening Day healthy, giving Showalter flexibility to maneuver arms as he saw fit.

Showalter’s first decision of the season was to bring in Smith, who allowed a leadoff double to Jorge Soler to bring the tying run to the plate. After a flyout, Smith struck out Bryan De La Cruz and Jacob Stallings in succession, punching out Stallings on a 96-mph fastball above the zone.

“That’s a pitch that is going to help me out a lot this year,” Smith said, noting that Verlander has been encouraging him to use it more often. “I think I just need to trust it more.”

Next up was Raley -- an offseason trade acquisition and the lone left-hander in the bullpen -- who struck out a pair in a perfect eighth inning. Robertson, a relatively modest piece of the team’s offseason spending spree, followed with an equally flawless ninth. The result improved the Mets to 41-21 all time on Opening Day, which is by far the best record of any Major League franchise.

“They did exactly what we expected out of them,” Robertson said of Smith and Raley. “They’ve both got electric stuff. They came in there and filled up the zone, got big strikeouts when they needed to. We just pushed the ball to the next guy in line and managed to come up with a win.”

Ultimately, Showalter acknowledged, the Mets’ bullpen challenge will continue well beyond Opening Day, as the team deals with additional injuries and attempts to keep its healthy relievers as fresh as possible. While Robertson figures to receive the bulk of save chances, Ottavino, Raley and Smith should also see their share.

“I thought the guys showed a lot of mental fortitude and toughness today coming into those roles,” Nimmo said, “and accepting them and succeeding in them.”

For the foreseeable future, the Mets will lean on this group, knowing they can always canvass the midseason trade market if they need to. Their relief corps may be depleted sans Díaz, but it certainly isn’t broken.

As long as that’s the case, Showalter can spend his sleepless hours pondering things other than a bullpen that doesn’t currently qualify as a problem.