HOUSTON -- First, the Red Sox lost David Price just 15 pitches in on Saturday night when manager Alex Cora made the decision to pull him due to flu-like symptoms. Then, they lost hold of the game even after they came storming back to tie it the top of the ninth.

The momentum was short-lived as Matt Barnes loaded the bases with nobody out to start the bottom of the ninth, and he gave up a walk-off single to right by Carlos Correa in the bottom of the ninth that completed a crushing, 4-3 loss to the Astros.

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Down 3-1 in the top of the ninth, Christian Vazquez came up big for the Sox with a two-run single against Astros closer Roberto Osuna.

At that moment, the Red Sox were feeling great about their chances to win, with runners at the corners and nobody out.

But it was not to be. Here is the anatomy of what wound up a difficult loss that dropped Boston 7 1/2 games back in the American League East for the first time since April 29:

Baserunning blunder short-circuits rally

Boston’s bullpen came up big after Price’s quick exit and the Red Sox were trailing just 2-0 in the top of the seventh.

All they needed were some big hits. Andrew Benintendi trimmed Boston’s deficit to a run when he laced an RBI single to center. They were looking for another hit right after that from Mookie Betts, their best all-around player.

But in a surprising turn of events, Betts had the bat taken right out of his hands. This was due to his teammates -- J.D. Martinez and Benintendi -- getting caught up in an unfortunate rundown when a pitch by Ryan Pressly went into the dirt and briefly got away from catcher Robinson Chirinos.

As Chirinos pounced and made a quick recovery, Martinez, who had strayed toward third base, hustled back toward second. Benintendi, as the trail runner, did what he is taught to do and took off when he saw Martinez do so. Martinez was tagged out and Betts was deprived of his big chance.

“It’s one of those where you make the read,” said Cora. “I talked to J.D. It’s a tough one on him because obviously he doesn’t want to get thrown out at third, but when you take off with a man on first he’s going to follow you. If you make a decision, you just keep going. It’s one of those he made up his mind and halfway through he’s like ‘Oh, I’m not going to make it,’ so at that time Benny’s going to follow you. The runner at first is at your mercy at second so it just didn’t work out.”

Another missed opportunity

Vazquez’s well-placed, well-timed two-run hit down the line in left in the ninth set up his teammates to lead what could have been a big win.

But Jackie Bradley Jr. was stranded at third when Osuna struck out Steve Pearce, got Benintendi on a short popup to third and Mitch Moreland on a groundout.

It was another example of the Red Sox not doing the little things as well as they did last season.

“Situational hitting,” said Cora. “We’ve got to put the ball in play there. First and third, we’ve got to put the ball in play and we didn’t. We have to at least drive the ball through the infield. We didn’t do the job and paid the price.”

Barnes has rare misstep

Barnes has been Boston’s best reliever all season and came into the game with a 1.80 ERA. In other words, he just picked a bad night to have a mishap.

It started right away in that bottom of the ninth when Aledmys Diaz rifled a double to lead off the inning. Barnes had to be careful with the dangerous Alex Bregman and he walked him. What really hurt was the walk to Michael Brantley that loaded the bases and put Correa in an ideal position to punch one through a drawn-in infield, which he did to give the Astros the win. For the first time this season, Barnes didn’t record any outs.

“Yeah, I just stunk,” said Barnes. “I mean, flat-out, couldn’t command stuff. I left a 1-0 breaking ball to Diaz and he ripped it inside for the double. I made some pretty good pitches to Bregman. I thought there was one fastball, threw a good curveball, he spit on it and he’s a good hitter. Just didn’t execute enough pitches. Left stuff over the middle of the plate and wasn’t around the plate enough. You know, it’s on me, got to be better and it just sucks.”

For the second straight weekend, the 35-18 Astros have taken the first two games in a series between MLB’s past two World Series champions. The Red Sox (27-25) will try to salvage the finale on Sunday afternoon like they did last weekend in Boston.

“You’re talking about one of the best teams, if not the best team in baseball right now on the other side,” said Barnes. “Up and down the lineup from offense to their pitching, they’re a really good team and so are we. You’re talking about the last two world champions. There’s not going to be too many lopsided games when we’re playing each other, regardless of where it is. They’re always going to be tough, fought-out battles and unfortunately I didn’t do my job tonight to get us the win.”