NEW YORK -- The weekend of opportunity is turning into a lost one for the Red Sox.

The clutch hit was again elusive, as was the ability to prevent the Yankees from getting them.

A 5-3 defeat put the Sox back at .500 (29-29) for the first time since May 9, and dropped them to a season-high deficit of 9 1/2 games in the American League East.

• Box score

It isn't as if the defending World Series champions are in panic mode. But there is definitely a sense that things need to start changing swiftly. By losing six of their last eight, and four in a row, the Sox have washed away the momentum they built by reeling off a 12-3 stretch from April 29-May 15.

"Yeah, we're not closing the gap," said losing pitcher Rick Porcello. "We're making it bigger -- it's tough. We were in a tough spot coming in, we're in an even worse spot now and we've got to be ready to fight every night. That's the bottom line. Everybody. All cylinders, 25 guys got to be ready to win ballgames each and every night and we don't have a whole lot of room to wait around at this point. We've got to go."

The Yankees, despite their many injuries to key players, are in first place. They are also 4-0 against their rivals this season after winning the first two games of this three-game series. In those four defeats to New York, the Sox are hitting .208, including 2-for-22 with runners in scoring position.

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"They've played well," said Red Sox manager Alex Cora. "We haven't hit. I think we're like 2-for-24 with men in scoring position against them. That should change. We've got talent and we've got a good offensive club. Just keep making adjustments and hopefully it starts [Sunday]."

The hope was that it would start on Saturday.

But Porcello picked a bad night to have his worst outing in weeks. The righty was touched up for nine hits and five runs over 4 2/3 innings. He walked one and struck out five. In Porcello's previous eight starts, he was 4-1 with a 2.94 ERA, with his team going 7-1 in those games.

The Yankees snagged the early momentum with three runs against Porcello in the second to take a 3-1 lead. The Sox battled back in the fourth as Xander Bogaerts ripped a solo shot and Sandy Leon had his second RBI single of the night to tie it up.

But Gary Sánchez, who never seems to tire of tormenting Boston, unloaded for a two-out, two-run homer on a 2-2 slider by Porcello in the fifth.

"I think the biggest at-bat, obviously, was the Sanchez at-bat," said Porcello. "Our offense did a hell of a job grinding back. [Domingo] German has been throwing the ball great this year and I just can't let it happen. It was the worst possible result in that at-bat and looking for anything other than giving up a long ball there."

Still, the Red Sox had chances to come back. In fact, they had two chances with their best pure hitter at the plate.

With two on and two outs in the sixth, the Yankees brought in Adam Ottavino to face J.D. Martinez. The tough righty won the battle by whiffing Martinez on a nasty 1-2 slider to end the inning.

In the ninth, the Sox had a promising start against closer Aroldis Chapman when Mookie Betts walked and Andrew Benintendi smacked a single.

Once again, Martinez was the go-ahead run. But Chapman threw a 1-0 slider on the outside corner and Martinez tapped into a crushing 6-4-3 double play to thwart the rally.

In his last 40 at-bats, Martinez is hitting .175 with a .667 OPS.

"Yeah, I feel like every now and then there's a couple at-bats where it gets away from me but for the most part I feel like I'm sticking to my plan," Martinez said. "It's just, I'm not really getting results."

He isn't alone. In Saturday's game, the Sox went 2-for-14 with runners in scoring position.

"We've been talking about this for like a week," said Cora. "There's always traffic and all that, but we're not getting that big hit. Today, Sandy was the only one who got hits with men in scoring position. We struck out too much today. Sometimes it's a credit to them. Sometimes it's just we're expanding the zone. We don't do that often, but it seems like the last 10 days, with men in scoring position, we haven't done much."

Now at a critical point in their season, the Red Sox know that there are many things they need to improve on.

"It's not going to come easy for us, especially what we did last year, we're going to have a target on our back every night and we've got to be prepared to meet that challenge," said Porcello. "We've got to clean everything up -- to pitching, to baserunning, to fielding, to hitting. It's all facets of the game right now we've got to get better. We've all got to lock in and get going."