The Rangers appeared to be in trouble when they fell behind 3-0 with Felix Hernandez on the mound for Seattle. But they got to the ace for three runs in the fifth and added three more against the Mariners' bullpen.
Singles from Moreland, Donnie Murphy and Leonys Martin loaded the bases with no outs in the fifth. Robinson Chirinos drew a walk on four pitches to push Moreland across for the Rangers' first run. Michael Choice singled in another run and Elvis Andrus' sacrifice fly tied it at 3.
Hernandez allowed five hits in six innings. He struck out four and walked three. Charlie Furbush (0-2) got the loss.
After Moreland's sacrifice fly gave Texas the lead, the Rangers added a pair of insurance runs in the ninth against Joe Beimel. Martin scored on a wild pitch and Fielder singled in Andrus.
In the leadoff spot for the first time this season, Michael Saunders homered off Colby Lewis to give the Mariners an early 1-0 lead. Kyle Seager led off the second with another homer and then scored on Mike Zunino's sacrifice fly in the fourth
NOTES: Texas is expected to activate LHP Matt Harrison from the 15-day disabled to start Sunday's series finale. Harrison hasn't appeared in a game since April 6, 2013. Harrison was the opening-day starter for Texas last season but only made two starts before landing on the disabled list in need of surgeries to his back and torso. He won 18 games for the Rangers in 2012. RHP Brandon Maurer (0-0, 2.08 ERA) will start for Seattle ... It was Saunders' third career leadoff homer.