The Rays' rookie has won all three of his starts against Seattle, allowing just two earned runs over 22 1-3 innings.
"He's been really good," Mariners manager Eric Wedge said. "He just keeps the ball down. The only time he comes up is when he wants to. Yeah, he's a good looking young pitcher."
Mariners starter Charlie Furbush (3-5) gave up five runs and eight hits in three innings. The left-hander has allowed 12 runs over seven innings in his last two road starts.
"I just wasn't throwing good enough pitches," Furbush said. "I was leaving some balls up in the zone and just wasn't executing."
Furbush has dropped all four career road starts, giving up 28 runs in 21 2-3 innings.
Seattle has lost four in a row. The Mariners, who entered hitting a major league-low .231, didn't advance a runner past second base until one-out in the eighth.
Longoria finished with four RBIs, including a two-run homer in the first. He joined Hall of Famer Eddie Mathews as the only major league third basemen to have 20 or more homers in each of their first four seasons.
Hellickson (11-8) was coming off the shortest start of his 32-game career, a 9-2 loss last Saturday to the New York Yankees in which the rookie gave up four runs and eight hits in 4 1-3 innings.
Joel Peralta pitched the ninth and completed a seven-hitter for the Rays, who have won nine of 11 and improved to a season-high 12-games over .500 (68-56).
After Johnny Damon tripled, Longoria put the Rays ahead 2-0 on a two-run shot off Furbush during the first. Longoria has 59 RBIs over his last 60 games.
"It was a fastball," Furbush said. "I was kind of hoping he wasn't going to swing, you got to tip your hat to him. On a 3-0 pitch he is going after the ball."
Elliot Johnson had an RBI single and Longoria drove in a pair with a single that made it 8-0 in the eighth.
Ichiro Suzuki had been hitless in nine at-bats, including his first three plate appearances Saturday, against Hellickson before getting an eighth-inning single off the right-hander.
"I have no idea," Hellickson said about his success against Suzuki. "I just locate well, I guess. I think he gets himself out more than I've got him out."
Seattle first baseman Mike Carp extended his hitting streak to 19 games with a single in the fourth.
Mariners shortstop Luis Rodriguez got hit on the right elbow by Hellickson's pitch in the second and left the game after running the bases. Wedge said the infielder is day to day.
NOTES: The Mariners have been shutout 11 times this year.. ... Seattle SS Brendan Ryan, who returned Friday after being out with a sprained left shoulder joint, could be back in the starting lineup in the next couple days. ... Tampa Bay RHP James Shields (11-10) will look to increase his major league-best nine complete games this season on Sunday. .... Mariners RHP Michael Pineda (9-7), Sunday's scheduled starter, leads all AL rookies with 143 strikeouts. Opposing batters are hitting just .209 against him. ... Kotchman was credited with a seventh-inning infield single in Friday night's game as part of a scoring change. Mariners 3B Adam Kennedy had originally been charged with an error for misplaying Kotchman's grounder.