Catcher Rob Johnson followed with another run-scoring hit and the Mariners coasted from there for a 5-3 victory over their division rivals before 33,220 at Safeco Field.
Seattle (46-42) won the series, 3-1, and remained four games behind the American League West-leading Angels. The Mariners closed to within 2 1/2 games of the Rangers.
"I don't think anyone wants to head into the All-Star break losing a ballgame," Rangers manager Ron Washington said.
The mood inside the home clubhouse was much different.
"To win the series and take three out of four from a team like Texas is always special," manager Don Wakamatsu said. "This team has a lot of character and a lot of fight, and it showed again today."
The Mariners had two outs and none on in the seventh when Ken Griffey Jr. reached on an infield single. Franklin Gutierrez singled up the middle, advancing pinch-runner Josh Wilson to second, and Shelton lofted a single over shortstop Elvis Andrus' extended glove.
Shelton, batting for Ryan Langerhans, said his primary mission was to "have a quality at-bat, and I felt like I did that. Fortunately, I got enough of it that I hit it over the infield."
The Mariners never trailed in the series finale, but lost a three-run lead in the sixth inning when the Rangers hit two home runs. But after the third one, which tied the game at 3-3, Seattle relievers Miguel Batista, Mark Lowe and David Aardsma retired 10 of the final 11 batters they faced.
Batista notched the win in relief of starter Erik Bedard and Aardsma nailed down his 20th save in 22 save chances. Not bad for a guy who started the season with no career saves at the big league level and a setup man for then-closer Brandon Morrow.
"I definitely wasn't expecting [20 saves] coming out of Spring Training," Aardsma said.
A lot of unexpected things happened during the first 14 weeks of the season, so much so that right fielder and All-Star Game-bound Ichiro Suzuki said after the game, "For me, it is just so much fun right now.
"Compared to last year and the past few years, at this point of the season we were already in a casket."
The Mariners went into the three-day All-Star break last season with a 37-58 record and 20 games out of first place, finishing the season with 101 losses.
On Sunday, two swings took care of the Mariners' three-run lead in the sixth inning.
Hank Blalock socked a two-run home run off Bedard and Nelson Cruz greeted Batista with a first-pitch home run to right field.
Ichiro Suzuki noted one of the main differences between the Mariners this year as opposed to past seasons.
"Compared to the last few years," Ichiro said, "the clubhouse atmosphere is incomparably better."
Shelton has noticed the same thing.
Though he spent most of Spring Training with the team, he arrived from Tacoma last week unsure of how he would be welcomed. For one thing, he is not a particularly outgoing person.
But he immediately became one of the guys.
"They welcome you and make you feel relaxed, which is nice," Shelton said. "They want you to go out there and what you are capable of doing, nothing more and that always makes the person coming in feel at ease and fit right in."
That goes for first-time players or veterans.
The Mariners got re-acquainted with left-hander Erik Bedard, who bobbed and weaved his way through 5 2/3 innings and ended up with a no-decision.
Two swings took care of the three-run lead Bedard took into the sixth inning.
"He didn't pitch as well as we'd liked today, but he battled," Wakamatsu said. "It didn't seem like he had the feel for his curveball. His stuff is electric and he pitched out of quite a few jams."
Double plays in the first and second innings bailed Bedard out of trouble.
After striking out the first batter he faced since June 7, Bedard walked the next two. He had a 3-0 count on Andruw Jones, who received the green light, swung away and hit a sinking line drive to center field.
Michael Young, apparently thinking the ball would drop for a hit, sprinted to third base. But Franklin Gutierrez, who has played superb defense all season, charged in and made a diving catch, got to his feet and doubled up Young at second.
Bedard ran into more trouble in the second inning when back-to-back singles put runners on first and second bases with none out. Cruz struck out and Taylor Teagarden grounded into an inning-ending double play.
"We had Bedard in trouble all day. We just couldn't punch anything across," Washington said. "He made pitches when he had to, but when you get a guy like that out there putting people on the bases, you gotta try and take advantage of it. It was him making pitches and us not putting them in play properly."