SEATTLE -- The script on what was shaping up to be another sleepy night in Seattle awoke vigorously Tuesday and wrote itself in an absolutely -- and almost unbelievably -- unreal way.

The matchup: The Mariners' Abraham Toro against the Astros' Kendall Graveman, the key pieces in a polarizing trade that, despite the Mariners’ topsy-turvy performances since, has come to define the second half of their season.

The stakes: A bases-loaded, eighth-inning sequence of a scoreless tie game, one that Seattle was clinging its postseason hopes to with the calendar trimming.

On the eighth pitch of that nail-biting one-on-one, Toro crushed a 98.6 mph sinker from Graveman that was running away from the switch hitter, in the upper third of the strike zone, and crushed it 413 feet beyond the deepest part of right-center field.

The new Mariner of five weeks briefly paused to watch the ball’s flight, while the former linchpin of Seattle’s bullpen one-hopped the front side of the mound in unison with the sound of the ball off the bat, a sign of defeat.

In essence, they both knew immediately that Toro’s first career grand slam was on its way to lifting the Mariners to a 4-0 win at T-Mobile Park, one that they so badly needed, at least from a morale standpoint.

“It's crazy how this game, things work out and things line up, where the two guys that were traded for each other and the game's on the line,” Mariners manager Scott Servais said. “Unbelievable at-bat by Toro to hang in there against Graveman, and he got one that he didn't miss and put a heck of a swing on it.”

Graveman initially looked like he wasn’t even going to enter the game. Cristian Javier was warming before Astros manager Dusty Baker instead opted to call on “Big Heavy,” as his Mariners teammates used to call him, to get ready for the top of Seattle’s order, after Paul Sewald -- for the second time in 10 days -- struck out the meat of Houston’s order in the eighth.

But Graveman was called on to face a lineup that had looked lifeless to that point, stranding six runners in seven innings to bring their total to 53 for the homestand.

Yet the Mariners found a spark. J.P. Crawford drew a nine-pitch walk, Graveman’s good friend, Kyle Seager, pulled a single into right field, then Ty France took a 98 mph running fastball off his right wrist, all of a sudden loading the bases for Toro.

A one-on-one that seemed too dramatic to imagine had quickly presented itself.

“I actually looked at my lineup card [before the inning], and I said, ‘These guys are going to hook up,’” Servais said.

Then came the actual matchup. Toro immediately fell behind 1-2 after taking a pair of huge swings over two high-90s fastballs, but by that point, he had his timing. The advantage was working in his favor.

“The longer the at-bat went with Toro, you felt really good something was going to happen,” Servais said.

Graveman shifted to a four-seamer that led to a foul. Then back to a sinker for a ball. Another sinker for a foul. Then he unveiled a slider attempting to secure the punchout, to yet another foul.

“Before that, I was just really trying to swing as hard as I could,” Toro said. “And that's why I was under the baseball. And then when I got to two strikes, I just kept it simple, stayed straight to the baseball.”

Toro knew after the slider that he’d worked himself back into a fastball count. He was simply looking to hit a sacrifice fly in that moment, but watching five sinkers to that point helped him time his barrel up.

“I tried to go back off the front hip with a sinker and just missed a little bit on the plate,” Graveman said. “He did a good job getting the barrel there. He’s put together some good at-bats against us. He’s a good player. For me, personally, I wouldn’t change anything really that about that at-bat, maybe a little bit further in on that last pitch. Tip your hat.”

The fate of it all is what made the totality of the moment all the more surreal. Thirty-six days prior on this very field, an emotional Graveman couldn’t hold back tears when speaking with reporters about the trade that left him stunned -- and many in Seattle’s clubhouse upset. Yet after the immediate dust settled, both have gone on to become positive additions for their acquiring clubs.

The Mariners, who with the win moved to 3 1/2 games out of the second American League Wild Card spot with 29 games to play, still have another three-game series in Houston next week, not including Wednesday’s series finale.

Given the weight of their trade, Graveman and Toro always seemed destined to face off, but if they do again, it’ll be almost impossible to top the drama of their first encounter.