BOSTON -- After scoring six runs or more in their first four games, the bats finally went cold for the Red Sox in a 4-1 loss to the Pirates on Tuesday night at Fenway Park.

In Wednesday’s series finale, Boston needs a win to salvage a game in this three-game set against the Bucs and to earn a 3-3 split in the opening homestand.

Here is a look back at three pivotal elements of Tuesday’s defeat.

McGuire can’t hang on, Pivetta pays
The key play of the ballgame was what should have been the final pitch of a 1-2-3 second inning for Red Sox starter Nick Pivetta.

The Boston righty threw a curveball that Canaan Smith-Njigba swung right through. Unfortunately, the pitch somehow went through catcher Reese McGuire’s mitt for what proved to be a pivotal passed ball. Three pitches later, Ji Hwan Bae struck for his first career homer, putting the Sox in a 2-1 hole.

“He made a really good pitch,” said McGuire. “It was just nasty enough to get right underneath my glove. I felt like I was in a good position to get ready to lift it up into the zone, and for whatever reason, it just kind of clipped off the end of my glove and I didn't quite get down to it. Complete ownership of that. It always sucks, the next batter leaves the yard and you feel like that inning should have been over.”

There was one thing for which McGuire was second-guessing himself after the game.

“The one takeaway I think I can get from it is that I probably should have slowed the game down and taken a mound visit [after the passed ball],” McGuire said. “I feel like that would have helped myself, but also in that situation not let that momentum just go right into the next pitch. It’s a good learning point, but it sucks that it had to be that way.”

McGuire has taken some early-season lumps while getting his first chance to be a team’s primary catcher. In the three games he’s caught, opponents are 12-for-12 in stolen-base attempts. Obviously, the pitching staff is responsible for a considerable share of that. The Pirates stole twice on Tuesday, including one by catcher Tyler Heineman that led directly to an insurance run.

“I take pride in throwing guys out. I need to do a better job of making a more accurate throw,” said McGuire. “I’m looking forward to the next opportunity these guys run, because the arm is starting to feel better, honestly. The weather is getting a little bit warmer. So I feel like the first series was obviously cold and it was a little tough to get a grip on the ball, but I think moving forward, obviously we've already done a good job of making adjustments on the mound with our times to the plate.”

First turn through rotation not pretty
Pivetta’s stat line of five innings, three hits, three runs (one earned), three walks, six strikeouts and two homers allowed was the best in the first turn through the rotation.

Starting with Corey Kluber’s second turn on Wednesday, the Red Sox need to get better production from their starting pitching. In its first five starts, Boston’s rotation logged just 20 1/3 innings, allowing 29 hits, 23 earned runs and 12 home runs.

“Everybody knows it,” said Red Sox manager Alex Cora. “There’s no secret. We have to pitch better. Today, although [Pivetta] went five, I thought he was good. He gave us a chance. Tanner [Houck] gave us a chance [on Sunday]. We just have to be better. We have the guys. We’ve got Corey tomorrow. Finish this homestand with a ‘W’ and move on.”

One last chance to cool off Reynolds
Dating back to last August, Pirates center fielder Bryan Reynolds has destroyed the Red Sox the past four games he’s faced them, going 11-for-17 with six homers and 10 RBIs. If the Pirates can’t work out a contract with Reynolds, perhaps the Red Sox should target him in a trade.

On Wednesday, they will get one last chance this season to try to stop him.

“He’s been a great hitter in this league for a few years now,” said McGuire. “We’ve just got to  keep getting a little creative and figure out ways to get strike one on him but also limit his damage. He’s a tough out right now, but there are definitely moments we can go about the at-bat a little bit differently. So we're going to make those adjustments.”