The rookie allowed three straight singles to open the frame before exiting. With the game knotted up at 1, Ellis welcomed Hansel Robles out of the bullpen by drilling a two-run double over the head of left fielder Curtis Granderson, and the Phillies went on to score two more runs in the inning.
"[Gsellman] was cruising along," Mets manager Terry Collins said. "He made some pitches and got some ground balls. He had a pretty low pitch count ... and I thought he was pitching pretty good. Unfortunately, he gave up the three hits."
Despite the loss, the Mets remained 2 1/2 games back of the second National League Wild Card spot as the Cardinals lost to the A's.
Phillies starter Vince Velasquez wasn't efficient, needing 103 pitches to get through five innings, but he was effective. The right-hander surrendered only one run -- a Granderson sacrifice fly in the first -- on five hits while striking out seven.
"We've had periods like that, where we got beat pretty bad and that's one of the things these guys have done -- they put it behind them," Phillies manager Pete Mackanin said, referring to the Phils losing the first two games of the series by a combined 21-5 margin. "They've been resilient. They came back and played baseball. That's a testament to the guys. They play hard."
The Mets lost shortstop Asdrubal Cabrera, who left the game with a sore left knee in the first inning following a first-base collision with the Phillies' Tommy Joseph.
MOMENTS THAT MATTERED Welcome, A.J.: The Phillies acquired Ellis in the Carlos Ruiz trade with the Dodgers on Thursday, he joined the team Saturday and he appeared in his first game Sunday. He went hitless in his first two plate appearances before he ripped a double to left field with the bases loaded and no outs in the seventh. Ellis' double scored two runs to give the Phillies a 3-1 lead. He later scored on a sacrifice fly to give the Phillies a 5-1 lead.
"It felt good regardless of what's happened in the last four days," Ellis said. "It feels good to drive in runs, feels good to help put your team ahead and help contribute to a team win." More >
Solved the puzzle: Up until the seventh, the Phillies were having a difficult time getting a good swing off Gsellman. In those six innings, Philadelphia hit just three batted balls that had exit velocities greater than 100 mph, according to Statcast™. The right-hander tossed a perfect fifth and sixth and entered the seventh with only 84 pitches, but the Phillies apparently figured him out. The singles off the bats of Tommy Joseph, Aaron Altherr and Jimmy Paredes in that frame clocked in at 109 mph, 109 mph and 100 mph, respectively.
Finally, Vince: It has been a rough few weeks for Velasquez, who posted a 10.47 ERA in his past three starts and a 7.29 ERA in his past six. But after he worked out of jams in both the first and second innings against the Mets he retired 12 of the final 14 batters he faced to give him his best start in more than a month.
"I guess it's just a step in the right direction," Velasquez said. "I had another high pitch count, another long first inning, but I battled my way through it and made my pitches." More >
"I told these guys when I came in, the one thing you know about the Phillies is if they get a lead late, the game is over. [Edubray] Ramos, [Hector] Neris and [Jeanmar] Gomez. The game's over. Those guys are lights-out. We saw it firsthand in L.A., and I got to see it behind the plate today." -- Ellis
SOUND SMART WITH YOUR FRIENDS
Phillies setup man Neris struck out one in a scoreless eighth. He is 3-0 with a 1.13 ERA in his past 31 appearances.
Phillies shortstop Freddy Galvis stood on third with one out in the third, when Cesar Hernandez dropped a bunt up the third-base line. Mets third baseman Jose Reyes threw to first and first baseman James Loney threw to the plate to get Galvis for an inning-ending double play. Why was Hernandez bunting there?
"When you're swinging the bat well and getting hits, I'd prefer for him to swing the bat," Mackanin said. "He's swinging the bat as well as anybody we have. But I'm not going to fault him for it. If he gets the bunt down the third-base line, then he gets the run in. I'd prefer him to swing, but what he did I can't criticize him for."
WHAT'S NEXT Phillies: Phillies right-hander Jake Thompson (1-3, 9.78 ERA) has struggled in each of his first four big league starts, unable to pitch more than five innings in any of them. He faces the Nationals in Monday's 7:05 p.m. ET series opener at Citizens Bank Park.
Mets:Rafael Montero makes his first start this season, opposing Marlins ace Jose Fernandez on Monday at 7:10 p.m. ET at Citi Field. Montero is filling in for Jacob deGrom, who is being skipped so that he can work on fixing mechanical issues. Montero struggled mightily at Triple-A Las Vegas and was reassigned to Double-A Binghamton on July 14. Since that move, the right-hander has gone 4-2 with a 1.70 ERA in eight starts.