By MATT BECKER
(AP) -- A postseason berth could be secured over the weekend for the Texas Rangers, who are also inching closer to winning a third straight AL West title.
While reaching the playoffs doesn't seem like it should be an issue, the team suddenly has concerns over the health of its All-Star center fielder.
Bothered by a sinus problem, Josh Hamilton is returning to Texas for further examination while the Rangers head to Seattle to open a series with the Mariners on Friday night.
Hamilton, the major league leader with 42 homers, has missed Texas' last two games with a recurring sinus problem that makes it tough for him to breathe.
"The last five or six days I've been battling something," the slugger said before Thursday's finale with the Los Angeles Angels. "Sometimes it can cause me to be off-kilter, off-balance, but this is the first time it's caused me not to be able to focus the way I want to on the field.
"The more you run when you can't breathe as good, you get a little dizzy, a little thrown off."
The Rangers (89-60) aren't taking any chances with his health, sending the 2010 AL MVP back to Texas to meet with team doctors.
Adrian Beltre sat out Wednesday's 6-2 win over the Angels with abdominal discomfort and wasn't in Thursday's initial lineup, but talked his way into the cleanup spot as a designated hitter. He went hitless his first three at-bats, but with one on and nobody out in the ninth in a 1-all game, Beltre crushed a two-run homer, lifting Texas to a 3-1 victory.
"This is the time of year you want to play," said Beltre, who has now homered four times in eight games and leads the majors with nine this month.
The Rangers remained four games ahead of second-place Oakland with 13 to play, and their magic number over the Angels to snag a wild card is down to five.
Texas took two of three from the Mariners at home last weekend.
Seattle (70-80) got a much-deserved off day Thursday after combining to play 29 innings in consecutive games against Baltimore. Unfortunately for the Mariners, both were losses, and with Wednesday's 3-1, 11-inning defeat, Seattle dropped its fourth in a row and ninth in 12 games.
The Mariners have totaled eight runs during their skid, but have had plenty of chances, going 2 for 28 with runners in scoring position and leaving 35 men on base. Cleanup hitter Jesus Montero is batting .179 in his last six games.
"We're not doing anything offensively," manager Eric Wedge said. "The opportunities, the opportunities the people up there need to be doing better."
The Mariners couldn't get much going last weekend against Martin Perez (1-1, 3.38 ERA), who is set to make his first start since being called up from Triple-A Round Rock at the beginning of September.
Perez is taking the spot in the rotation of Scott Feldman, who has a 6.99 ERA in his last seven starts. After Feldman was tagged for six runs in 2 2-3 innings against Seattle on Saturday, the rookie left-hander came in and threw 4 1-3 hitless innings of relief.
Mariners probable starter Hisashi Iwakuma (6-5, 3.39) faced Texas last Friday, and the only runs he allowed came on solo homers to Hamilton and Ian Kinsler. He lasted 5 1-3 innings in a 9-3 loss. The rookie right-hander has lost his last two starts after going 4-0 with a 1.09 ERA in his previous five.
Kinsler is 4 for 6 lifetime against Iwakuma, and has four homers with nine RBIs and 12 runs against Seattle this season.
Updated September 21, 2012