NEW YORK -- The sweet sound exploded from Gary Sánchez bat, confirming instantly that he had gotten all of it. As he walked toward first base, the Yankees slugger admired the ball fading over the left-field fence, then flipped his bat toward the dugout before beginning his trot.

After a nightmarish start to the season, who could fault Sánchez for savoring the moment? Sánchez made history with that swing, becoming the first Yankee to belt a pinch-hit, extra-inning grand slam in the club's 5-2 victory over the Mets on Sunday at Yankee Stadium, completing a seven-inning doubleheader sweep.

"I've been very anxious to contribute to the team, especially when you're going through a rough patch," Sánchez said through an interpreter. "You're not helping the team, you're not producing for the team the way that I expect myself to. That's why I stood there and looked at the fly ball; because I understood that I was going to give my team a chance there."

Yankees manager Aaron Boone said that he favored the matchup of having Sánchez face right-hander Drew Smith, prompting the move to pinch-hit for Erik Kratz. Sánchez said that his focus was on selecting a pitch that he could drive to the outfield for a sacrifice fly, deep enough to bring Brett Gardner home with what would be the go-ahead run.

Sánchez worked the count to 2-2, fouling off a couple of fastballs and laying off a curveball and cutter, before Smith fired a 96.8 mph fastball up in the strike zone. Sánchez took a hack and didn't miss, launching it toward the left-field bullpen. Statcast projected the dinger traveled 453 feet and had an exit velocity of 108 mph.

"I wanted to go into the box looking to put a good swing on the ball," Sánchez said. "I understood that if I hit the ball well, a deep fly ball would give us one run and the lead. I was lucky enough to hit that, and it kept going."

Mets manager Luis Rojas said that "the fastball to Gary was 97 [mph], right after him being late on Drew's fastball. That was also a credit to Gary, getting the barrel out with the velocity of that fastball up there."

Sánchez's behind-the-scenes work could have paid dividends in this case. He said that he has been working with hitting coaches Marcus Thames and P.J. Pilittere, who have had Sánchez facing faster pitches to sharpen his timing.

"We're always talking, we're always communicating," Sánchez said. "I wanted high velocity from a pitcher so that I could get the head of the bat up front. That's one of the drills that we started doing and it's been working."

The Yankees have continued to support Sánchez throughout his struggles, with general manager Brian Cashman stating on Saturday that the 27-year-old remains the team's best option offensively and defensively.

"We are going with Gary Sánchez," Cashman said. "He is by far our best option on both sides of the ball. We look forward to him finding his groove sooner than later, because we need it. I still have confidence in the player. This is a unique season and you're seeing struggles from successful players around the game."

When Boone called his name as a pinch-hitter on Sunday, Sánchez carried a .123 average (10-for-81) to home plate, having slugged five homers with 37 strikeouts. He has also struggled behind the plate, continuing to work with catching coach Tanner Swanson on a one-knee-down approach intended to boost his pitch framing.

"We've all been there; you want to get some results," Boone said. "You want to come through in a big spot in the worst kind of way. Sometimes you've got to back off a little bit and just really focus on having good at bats and winning pitches.

"He went up there tonight and had a great at-bat, so I'm excited for him. He means so much to this team. I know how much he cares, and so I'm happy for him to really take the air out of one."