A day after the Mets sent Robinson Cano packing, two of the players who survived the roster crunch put their value on full display.

Travis Jankowski served as a spark plug as a fill-in leadoff man, using his speed to leg out two infield hits and score three runs, and Luis Guillorme flashed the leather in a start at shortstop.

Together, they helped the Mets knock off the Braves 5-4 in the first game of a doubleheader on Tuesday at Citi Field.

“[Jankowski was] excited as a guy going to his first game in little league, playing today and leading off,” manager Buck Showalter said between games. “Guys like him and Guillorme, they bring it in situations like this. … Trav’s been a pro, that’s why we wanted to keep him. He brings some tools that we need. He’s a great piece for us and good teammate and plays the game right.”

Pete Alonso also went 2-for-4 with a pair of RBIs, driving in Jankowski both times.

David Peterson, called up from Triple-A as the Mets’ 27th man for the doubleheader, started Game 1 and gave up four runs over five innings — a line that was blemished by Matt Olson’s three-run shot in the fifth inning. The bullpen then went on lockdown mode, as Adam Ottavino, Drew Smith (two innings) and Edwin Diaz combined to preserve the one-run lead to close out the game.

Guillorme, starting at shortstop with Francisco Lindor as DH, helped Peterson settle in early with a pair of impressive defensive plays against the first two batters of the game. He dove to his left to stab a hard grounder on one and then snared a chopper over the mound (out of the shift) and threw across his body for the out on the other.

“It’s amazing,” Peterson said. “It’s so much easier to pitch when you can pitch to contact and know that all eight of those guys have your back.”

Before the Mets (17-8) designated Cano for assignment on Monday, Jankowski and Guillorme loomed as potential cuts to get the roster down to 26. But Jankowski, the speedy fourth outfielder, would have been exposed to waivers and the Mets would have gotten worse defensively without Guillorme.

After Jankowski led off the bottom of the first with an infield single, Showalter called for and won a challenge that confirmed Lindor got hit on the left foot by a Charlie Morton curveball in the dirt.

Alonso then poked a single through the open right side of the infield to put the Mets up 1-0.

Eduardo Escobar came up next and lined a single to right field to score Lindor for the 2-0 lead.

Peterson issued a one-out walk in the second inning that eventually came around to score on a sacrifice fly to get the Braves (11-14) within 2-1.

But the Mets added to their lead in the bottom of the inning in a rally set up by walks to Guillorme and Jankowski. After Lindor drove in one run on a fielder’s choice with the bases loaded, Alonso came through again with a single drilled through the left side to make it 4-1.

Jankowski then made things happen again in the fourth inning. He beat out a double play, then stole second base and took third on Travis d’Arnaud’s throwing error trying to get him. That allowed him to score on Mark Canha’s sacrifice fly for the 5-1 lead.

“He knows the confidence we have in him and playing the game the way he plays it,” Showalter said.

The Braves cut into that lead in the fifth inning, when Olson crushed a three-run homer off Peterson to make it a 5-4 game. Olson’s blast came after Peterson had committed a fielding error on what could have been an inning-ending double play.