"We're hanging in there," manager Terry Collins said. "Cripes, we knew going in this was going to be a tough trip, and it is a tough trip."
Mejia, who has been pitching with varying levels of elbow pain all season due to bone spurs in the joint, allowed one run -- a Chris Denorfia RBI single -- in three innings, before grimacing on his second pitch of the fourth. He departed following a brief meeting with coaches and trainers, due to what the Mets termed "right elbow discomfort."
"I didn't want to keep pitching with that," Mejia said. "This bothered me a lot today."
From there, the game quickly unraveled. Though reliever David Aardsma was given all the time he needed to warm up, the Padres jumped on him for Nick Hundley's two-run homer and Alexi Amarista's RBI double to open up a three-run lead. An inning later, pinch-hitter Jesus Guzman touched Aardsma for an RBI single. Then Jedd Gyorko broke the game open with a three-run homer off Carlos Torres in the eighth.
Though the Mets knocked Padres starter Edinson Volquez out after five innings, driving his pitch count up to 100, they could not strike him for a game-changing blow. Instead, the Mets settled for isolated runs on Daniel Murphy's RBI single in the third inning and Ike Davis' run-scoring knock in the fifth.
After Davis' single, Wilmer Flores doubled, putting two men in scoring position with two outs for d'Arnaud. But in his third career plate appearance, the rookie grounded out to end the threat.
"I kept my focus and just tried to stick to the game plan," d'Arnaud said. "Unfortunately, we lost."
It was a disappointing result for d'Arnaud, who allowed a passed ball on defense and finished 0-for-2 with two walks. But the Mets remained far more interested in the long-term outlook for both d'Arnaud and Mejia.
In the case of d'Arnaud, Saturday marked the first part of a three-game trial to determine whether he will remain a big leaguer for the rest of the season. Regardless of whether he does, d'Arnaud represents a significant chunk of the Mets' future alongside pitchers Matt Harvey and Zack Wheeler.
Mejia is also critical to the future, considering he has established himself as a top-flight talent when healthy. But he has rarely been healthy over the past three years, preventing him from stepping alongside Harvey and Wheeler as an irreplaceable part of the organizational blueprint.
"I'm working hard, and now they know I can be a starter," Mejia said. "So I feel pretty happy with [what I did this season]."
But most important to Collins and the Mets right now is winning games. A Sunday victory with Harvey on the hill would put the Mets at 5-5 in the first 10 games of their longest road trip of the season, with one stop to go in Minneapolis. It would also ensure that they salvage something tangible from a trip that has been equal parts frustrating, worrisome and encouraging.
"We're trying to win," Collins said. "Let's face it, we're trying to fight back and do the best we can. If we win [Sunday], we're 5-5 going into Minnesota. The chance to have a winning record on the road is huge -- we play good on the road. We might as well continue to play good on the road."