The Mets could be missing two of the pillars that have propped up their an injury-ravaged season. In Friday’s 3-1 loss to the Nationals, both Yoenis Cespedes and Noah Syndergaard exited the game due to injuries.

Earlier in the day, the club announced that Matt Harvey will undergo season-ending surgery to treat thoracic outlet syndrome, adding to what has been a neverending stream of major injuries.

Cespedes was pulled in the fourth with what the team is calling a strained right quad. Syndergaard departed with two outs in the fifth after throwing his 79th pitch of the night.

The team did not immediately share details of Syndergaard’s injury. But his last three fastballs were clocked at 93, 93 and 91 mph, well off his season average of 98 mph. He has been pitching through a small bone spur in his elbow.

On Syndergaard’s 79th pitch of the night, he missed up and in with a 91 mph fastball. Catcher Rene Rivera jogged to the mound for a quick talk. He turned to return to the plate and Syndergaard appeared focused on making a 2-and-2 pitch when manager Terry Collins and trainer Brian Chicklo came to the mound.

After a conversation, all three walked off the field, leaving the fans at Citi Field squirming in their seats.

Meanwhile, Cespedes appeared to move awkwardly as he pursued Daniel Murphy’s double to the left-centerfield gap in the third inning. Two batters prior, he charged in to make a sliding catch. He briefly got tangled up with shortstop Asdrubal Cabrera at the of the slide, though both appeared fine in the aftermath.

Both Cespedes and Syndergaard are National League All-Stars. They’re scheduled to play in the Midsummer Classic on Tuesday, their reward for monster seasons.

Cespedes began the day hitting .303 wit 21 homers and 52 RBIs, even though he’s played through several smaller bumps and bruises. He was tied for fourth in the NL in homers and second in slugging (.585).

With Harvey’s struggles, Syndergaard has emerged as the staff ace. He entered his start 9-3 with a 2.41 ERA, the fifth best mark in the big leagues. His 8.20 strikeout to walk ratio is second in the majors.

Now, both face uncertainty, the latest jolt to a Mets team that has been besieged with health woes.

Third baseman David Wright is out for the year after neck surgery. First baseman Lucas Duda is still in the middle of length rehab for a stress fracture in his back.

Catcher Travis d’Arnaud only recently returned from a long DL stint with a strained rotator cuff and centerfielder Juan Lagares is playing despite a partial tear of a ligament in his left thumb.

Reliever Jim Henderson remains on the DL with right biceps tendinitis. And lefthander Steven Matz is pitching through a large bone spur in his left elbow, one that has forced the Mets to evaluate him start by start. The pain could prompt season-ending surgery at any time.

Zack Wheeler was expected to provide a boost for the Mets, with the end of his rehab from Tommy John Surgery coinciding with the start of the season’s send half.

But after enduring two setbacks, the Mets have avoided providing a timeline for Wheeler’s return.