But Bay's return to the lineup after a two-day mental health break accomplished little other than a bloop single in the fourth inning. He went 1-for-4 with two strikeouts.
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The key hit in the game was a two-run double in the third inning that was not played well by Murphy, who was making his second career start at the position.
Justin Turner -- the fill-in third baseman who Collins thinks is showing signs of fatigue -- got the night off. It might have cost the Mets the game on a night when five Pirates barely outpitched R.A. Dickey.
"That's a play I expect to make," Murphy said of Andrew McCutchen's double that hit off his right knee brace and bounded down the leftfield line for the eventual winning runs.
Murphy had time to get in front of the two-hopper to his right, but he misread it and tried to backhand it after sliding to the dirt.
It turned a 1-1 game into a 3-1 game and the Mets -- who went 2-for-11 with runners in scoring position and left nine men on base -- could not recover.
"My eyes lied to me right there," Murphy said. "Off the bat, it felt like a line drive that I was really going to have to give some ground with. I went to give ground with it, then I realized as I went down to the ground, it was off the end of the bat. I just didn't make the play."
Said Collins: "That's an error. No disrespect to Dan Murphy at all . . . He'll make that play the next 10 times."
That won't help Dickey (3-7), who was charged with three earned runs in an eight-inning complete game. But James McDonald (4-4) and four relievers were a little better.
"You hope the play is made," Dickey said. "Sometimes it is, sometimes it's not, and you've got to move on. Of course, I'd want it to be made."
The Mets (31-33), who had won five of six, failed to get to .500 for the first time since May 20, when they were 22-22 after beating the Yankees.
Saturday night's game was just a backdrop for a postgame concert by Huey Lewis and the News.
Pittsburghers -- and a good number of traveling Mets fans -- flocked to PNC for the event; the sellout crowd of 39,273 was the third-largest in the history of the ballpark, which opened in 2001.
The game was quick (2:19) but well worth the price of admission. The Mets had several chances to score, but the home team snuffed out the rallies.
Unfortunately for the Mets, Dickey was at the plate with the bases loaded and one out in the fourth and grounded into a 6-4-3 double play.
"That was a great baseball game," Dickey said. "It's painful and it ---- and I wish I would have won it, but it was a great baseball game."