WASHINGTON -- Over their storied careers, Jacob deGrom and Max Scherzer have combined to start 621 regular-season and postseason games. But with deGrom and Scherzer both unavailable on Opening Day due to injury, the Mets are turning to a pitcher who has appeared in only 18 Major League games.

Tylor Megill will start Opening Day for the Mets on Thursday in Washington, coming off a successful rookie season and a second consecutive eye-opening spring. The hard-throwing right-hander earned the nod because deGrom (stress reaction in his right scapula) and Scherzer (right hamstring soreness) were sidelined for the opener.

“I know it’s just another game, right? It’s one of 162,” Mets pitching coach Jeremy Hefner said. “But there’s the pageantry that comes with Opening Day and all those types of things that start the season. It’s special, and I’m glad he gets to experience that.”

Megill also earned the nod in part because he was arguably the Mets’ most outstanding pitcher this spring. In two Grapefruit League outings, Megill threw 6 2/3 scoreless innings with seven strikeouts, plus another 70-pitch outing on the backfields last Saturday. He is stretched out enough to throw up to 85 pitches in the opener.

“From the time I step on the field,” Megill said, “it’s go time.”

Bursting onto the scene after spending most of his first three years in the organization as a relatively unheralded prospect, Megill is coming off a rookie season in which he produced a 4.52 ERA with 99 strikeouts in 89 2/3 innings. Over that stretch, he has leapfrogged all the other depth options on New York’s 40-man roster, including fellow Opening Day candidates David Peterson and Trevor Williams.

“He can handle the situation, and I think we saw that last year,” Hefner said, “being able to navigate some pretty good lineups for two or three times through the order, six and seven innings at a time, finishing hitters, not walking guys, putting himself in good positions to be successful.”

Scherzer is scheduled to pitch Game 2 of the season, followed by Chris Bassitt, Carlos Carrasco and Taijuan Walker.

This should be an extended opportunity for Megill, with deGrom set to miss about two months. If Megill performs well in the opener and beyond, he could become a permanent member of the rotation.

Megill faced the Nationals twice last season, going 1-1 with a 4.91 ERA over 11 innings.

“We’re ready to go to work,” Hefner said. “It doesn’t matter who’s toeing the slab. We’ll be prepared.”