SEATTLE -- Jon Gray was signed prior to this season to be the ace of the Rangers, to lead a starting rotation that had some question marks and to give the team stability every fifth day.

In the midst of a brutal stretch of schedule in which Texas has lost one close game after another, the team needed Gray to set the tone on Wednesday afternoon against the Mariners and keep his team in the game.

He did it, and then some … until his last pitch.

A seventh-inning mistake on a slider to rookie sensation Julio Rodríguez led to a three-run home run and a 4-2 loss, and the Rangers left Seattle after being swept in three games by a total of four runs.

“All day long, he had wipeout stuff,” Texas manager Chris Woodward said of Gray. “So obviously that's a tough situation, to kind of go ahead and make a mistake there. I think the ball kind of slipped out of his hand. It was probably the only one all day, honestly. He was mowing people down, dominating. It just sucks for it to end that way.”

With the Rangers leading 2-1 in the bottom of the seventh, Gray issued a one-out walk to Cal Raleigh. He then gave up a double to Sam Haggerty, putting runners on second and third.

His approach to Rodríguez made sense, considering that the 21-year-old phenom has been crushing fastballs all year and had just come off a second-place showing in the Home Run Derby and his first appearance in a Midsummer Classic. Gray had already struck him out on a slider in the second inning, and gotten him out in the fifth on a groundout on which he began the at-bat with a slider.

This time he started with an 84.8 mph slider that Rodríguez took for a called strike. He threw another slider for a ball, and then he threw one more. It was 85.9 mph and at the top of the strike zone, maybe a bit high.

It did not matter to Rodríguez, who blasted it at 108.5 mph off the out-of-town scoreboard beyond the bullpens in left, a 416-foot shot. That was it for Gray, and after the Rangers’ bats went silent for the last two innings, that was it for Texas.

“We had a good plan and just didn’t execute one pitch,” Gray said. “[The pitch] didn't feel like my other ones. I don't know if I was trying to do too much there or what -- I’ll have to go watch some more film -- but it felt weird. I thought it might go over his head and go to the backstop.

“But he was swinging and it was in his zone.”

Gray was largely brilliant for the first six innings. In fact, he was throwing harder than he’s thrown all year. Gray entered the outing averaging 95.8 mph on his main weapon -- the four-seam fastball -- and he exceeded that all game.

He threw his 19 fastest pitches of the year, starting at 97.1 mph and only getting better, topping 99 mph twice.

That’s why Woodward never considered taking him out for the pivotal at-bat against Rodríguez.

“Jon Gray is built to be the guy that as a manager, as a coaching staff, we would never even consider taking him out of that spot, especially when he's still pumping 97, 98, and the life of the pitches is still there,” Woodward said. “So obviously we'll move on from that.”

Moving on from these nail-biter games that lately continue to end in the same fashion might seem like a broken record, but the Rangers have to be excited about Gray as the season progresses. The righty struck out eight in his 6 1/3 innings of work, and he was still topping 98 on the gun in the seventh inning. His fastball velocity has climbed steadily all season.

Mariners starter Marco Gonzales was stingy, too, however. The Rangers didn’t get a hit off of the lefty until the fifth inning, when Adolis García led off with a single, stole second, and then scored on an RBI double down the left-field line by Charlie Culberson. Texas added a run in the sixth when Elier Hernandez led off with a double and eventually scored on a two-out double by Jonah Heim.

The Rangers got some momentum in the eighth inning, putting runners on first and second with one out against reliever Erik Swanson, but Seattle righty Andres Muñoz came in and got two consecutive pop-ups to escape that threat.

They did it again in the ninth against Matt Festa, getting a single from Leody Taveras and a two-out walk by Ezequiel Duran, but Festa got Josh Smith on a groundout to end it.

Where do the Rangers go from here?

Well, Southern California. They’ve got a four-game series against the Angels starting Thursday on the next stop of this current 11-game road trip.

“Nobody likes to come in here and get swept,” Woodward said. “And these guys have played really well against us.

“So we’ll get on that plane, like I say all the time, and we’ve got to worry about Anaheim tomorrow.”