Even so, it was at least temporarily a demoralizing night for the Mets, who lost Bay on Jay Bruce's inside-the-park homer in the second. In his attempt to catch the ball near the left-field corner, Bay tumbled on the warning track and hit his head against the wall, lying still long enough for Bruce to race around the bases.
The victim of a previous concussion that cost him two months in 2010, Bay left the game under his own power but complained of dizziness at the time. Justin Turner should replace him on the roster in time for Saturday's game.
"It's really hard to watch, especially him just coming back from injury," said Scott Hairston, who subbed for Bay in left field and should see increased playing time in his absence. "He's a well-liked guy. We like having him around. It's very difficult to watch a player like that go through something like that."
Pressing on without their starting left fielder, the Mets fell into a four-run hole when Dillon Gee served up Brandon Phillips' two-run homer in the third. Though manager Terry Collins suggested that Gee may be feeling the effects of fatigue after logging significant innings early in the season, the right-hander blamed most of his trouble on simple lack of command.
"It was just a lack of execution on a couple of pitches that really hurt me this game," Gee said. "I've been throwing the ball well lately, and there are obviously some negatives you can focus on in this game. But really, I just want to stay positive and know that I've been throwing the ball well."
Throwing more effectively on this night was Arroyo, who did not allow a run until Kirk Nieuwenhuis drilled a solo homer off the facing of the second deck in right field in the sixth. Hairston followed with a two-run shot to left in the seventh, chasing Arroyo after six-plus innings of three-run ball.
But it was not enough for the Mets, who went down quietly in the final three innings against a trio of Reds relievers.
"I did pretty much what I wanted with their lineup," said Arroyo, who allowed just two hits over the first five innings. "I gave up two homers -- one on a hanging breaking ball and one on a pretty good pitch that was up and in. That's the way it goes. We had a comfortable lead, and those two extra runs were huge."
For the fans crowding into Citi Field, some of the only in-game excitement came in the eighth, when Sean Marshall responded to a Joey Votto plunking by drilling David Wright with a pitch. Although Collins and Gee both said that Votto's hit-by-pitch was unintentional, Wright understood what he considered a retaliatory move.
"We would have done the same thing," Wright said. "I appreciate him keeping the ball down and kind of doing it the right way. But that has to be expected. That's just guys policing themselves, and that's the way the game's played."
However the Mets play the game, they may need to grow accustomed to playing it again without Bay, who had appeared in just 22 games this season due to a fractured left rib. Bay also missed the final two months of the 2010 season with a serious concussion, making this latest injury seem all the more sinister.
It is hardly what one of Citi Field's biggest crowds of the season hoped to see. But for a Mets club that has overcome injuries and outperformed expectations throughout the young season, perhaps the fan base itself represented a bit of optimism on an otherwise dark night.
"Hopefully, people are jumping on board," Gee said. "Obviously, we lost tonight, but we're doing good things. Hopefully, we can string a few more wins together."