The AL West-leading Rangers, who have won 15 of 18 games, finished with a season high in runs after an eight-run eighth in which Profar had another RBI single.
Profar had a nifty slide to score on the bunt by Leonys Martin that dribbled only a few feet in front of the plate in that second-inning outburst. Seattle catcher Henry Blanco pounced on the ball and reached back trying to tag Profar, who made an elusive move to slide around and slap the back tip of the plate.
Rookie left-hander Martin Perez (6-3) pitched into the eighth to win his third consecutive start in August, even after giving up single runs in each of the first three innings.
Hernandez (12-6) had a season-high five walks and allowed five runs and five hits in five innings. The big right-hander, who threw eight shutout innings last Sunday against Milwaukee, came in as the American League ERA leader, but that mark went from 2.28 to 2.47 higher than the 2.41 for Hiroki Kuroda of the New York Yankees.
Adrian Beltre led off the Rangers second with an eight-pitch plate appearance. Beltre shouted out to Hernandez, his former teammate and good friend, while running to first base on his sharp single to center.
Texas loaded the bases with another hit and a walk before Profar blooped an RBI single and David Murphy hit a two-run double to deep center. Elvis Andrus added an RBI single after Martin's bunt for a 5-2 lead.
Hernandez hadn't allowed more than three earned runs in his previous nine starts since June 20. He is 0-3 with a 5.55 ERA in four starts against Texas this season.
Kyle Seager homered and had an RBI single for the Mariners, who have lost 13 of 20. He extended his hitting streak at Rangers Ballpark to 13 games since May 2012.
Perez had allowed exactly four hits in each of his previous three starts, including his first career complete game six days earlier.
The Mariners had four hits in the first two innings, when they built a 2-0 lead usually plenty for Hernandez. He was 103-25 with a 2.80 ERA in his previous 170 career starts when getting at least two runs scored for him.
Brad Miller led off the game with a double and scored on a single by Seager, who was picked off second base by Perez. Dustin Ackley had a single and stolen base in the second before scoring on Brendan Ryan's single. Seager's 19th homer, a 409-foot shot into the second deck in right field, came in the third.
NOTES: It was Texas' highest-scoring game at Rangers Ballpark without hitting a home run. The stadium is in its 20th season. ... Murphy's 16 career RBIs vs. Hernandez are more than any other player. ... Craig Gentry pinch-hit for the Rangers for the fourth game in a row, and reached each time. He had a pinch two-run double in the seventh, and added an RBI fielder's choice in the eighth in the No. 9 spot where Murphy started. ... Beltre is 6 for 12 this season against Hernandez. The Rangers third baseman, who played five seasons in Seattle, was 3 for 15 previously. Beltre almost had another hit, but 2B Miller made a nice backhanded play to finally end the second with runners at second and third. ... For the second night in a row, the Rangers had a runner thrown out for over-sliding second base. Ian Kinsler was out on what would have been a stolen base in the fifth.