Smoak's two-out hit off Joel Peralta (2-6) plated Kyle Seager, who had taken second earlier in the inning when Rays center fielder Desmond Jennings dropped a deep fly ball, with the eventual deciding run and enabled the Mariners to snap a string of six straight home losses in the opener of this three-game set.
"It feels good, especially in a 4-4 game with guys on base. It is always a good feeling to help out the team," Smoak said.
Seager knocked in two runs earlier in the contest, while Raul Ibanez belted a solo homer and Franklin Gutierrez went 2-for-4 with an RBI single.
The setback, the 10th in 13 outings for the slumping Rays, dropped the club to two games ahead of Baltimore and Cleveland for the AL's second wild card berth. The New York Yankees are 2 1/2 games back in the race.
Delmon Young finished 2-for-5 with a solo homer and two runs scored for Tampa Bay. Jose Molina also collected a pair of hits, including an RBI single.
"Working good at-bats has not been our problem. Getting guys on base has not been our problem, scoring them has been our problem. It is like having a bad red zone offense. We get close but just can't punch it through," said Rays manager Joe Maddon.
The Rays had tied the game at 4-4 on Luke Scott's pinch-hit double against eventual winning pitcher Carter Capps (3-3) in the top of the eighth, which came two batters after Wil Myers had reached via a single. Capps walked the next two to load the bases, but escaped further damage by getting Evan Longoria to ground out.
Jennings then was the culprit in perhaps the game's most pivotal play, as Seager's long fly to center popped out of his glove near the warning track to put the go-ahead run on second with one out. Peralta nearly atoned for the error by fanning Michael Saunders after walking Kendrys Morales, but Smoak drilled a liner to right that a sliding Myers couldn't come up with as both Seager and pinch-runner Abraham Almonte scored.
The Rays went down quietly against Danny Farquhar in the ninth, managing only a single as the Seattle closer nailed down his 13th save.
Seattle trailed 2-1 after starting pitcher Hisashi Iwakuma uncorked a wild pitch with the bases loaded in the top of the third, but countered with two runs in the bottom of the frame to move in front.
Dustin Ackley started things off with a leadoff single off Rays starter Alex Cobb before being erased on a forceout off the bat of Nick Franklin, who promptly stole second and moved to third on a groundout. Gutierrez followed with a base hit up the middle that knotted the score, then swiped second as well in front of Seager's go-ahead single to center.
Ibanez's 27th homer of the season, a towering blast to right to begin the bottom of the fourth, extended the lead to 4-2.
Tampa Bay pulled closer in the sixth when Young doubled and came around on Molina's two-out single through the right side that chased Iwakuma. Yoervis Medina came on to get Yunel Escobar to line out to left, however, stranding a pair of runners and keeping the score 4-3.
Iwakuma allowed three runs and eight hits over 5 2/3 innings.
Brad Miller snapped an 0-for-14 skid with a ground-rule double that began the bottom of the first and later scored on a Seager sac fly as Seattle grabbed an early 1-0 edge. The lead didn't last long, though, as Young clubbed a solo homer to open the second.
Tampa Bay took its only lead of the night in the third, loading the bases on consecutive singles by Ben Zobrist and Longoria and a walk to Matt Joyce before Iwakuma's slider got away from catcher Mike Zunino.
Cobb worked six innings, surrendering four runs on seven hits while striking out five.
Young's homer was his first as a Ray since Sept. 23, 2007 against Boston. The former No. 1 overall pick began his career with Tampa Bay before being traded to Minnesota of November of that year, then rejoined the organization in August ... Seager's RBI single extended his hitting streak to eight games ... Seattle improved to 19-12 in Zunino's 31 starts behind the plate ... The Rays have just two hits in their last 17 at-bats with the bases loaded.
09/07 03:24:27 ET