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5/22/2014 11:43 P.M. ET

Romero given look at DH against Astros righty

SEATTLE -- Mariners rookie outfielder Stefen Romero, who entered Thursday in a mini-slump, was batting seventh as the designated hitter against the Astros. Seattle will take a DH-by-committee approach until Corey Hart returns from the disabled list or the club chooses to make a roster move.

"We got to fill the DH spot some kind of way," manager Lloyd McClendon said. "Corey's out, so we're mixing and matching and hopefully we'll strike gold. We'll see."

Romero, a right-handed hitter, has posted a .209/.244/.360 slash line with two home runs and six RBIs in 30 games, while facing predominantly left-handers in a platoon role. However, he's shown flashes of promise. In a 12-5 win over the Rays at Safeco Field on May 12, the Oregon State product went 3-for-5 with a home run, double, three RBIs and three runs scored.

"I obviously want to be a little bit better statistically than where I am right now, but knowing my situation, I can't really get too down on myself with what role I have on the team," he said.

The Astros started righty Jarred Cosart (3-3, 4.41 ERA) in the series opener Thursday.

"DHing is a very difficult thing to do, and ideally you don't want to have young guys do it, but we are where we are right now, so we don't really have much of a choice," McClendon said.

Hart improving but rehab plan still uncertain

SEATTLE -- Mariners designated hitter Corey Hart said Thursday that his strained left hamstring is feeling better, after he injured it stealing second base during Sunday's 6-2 road win over the Twins, but he isn't sure when he'll begin his rehab process.

"I don't know if it'll be a week or maybe more before I can really start to move. Now, it's just ice and stuff," Hart said.

Hart flew back to Seattle on Monday and was injected with platelet rich plasma as part of a treatment aimed at alleviating muscle pain and accelerating the healing process.

"I can walk around without having to have a stiff leg all of the time. It's still nothing to be happy about yet," he said.

Hart, who the Mariners placed on the 15-day disabled list Tuesday, is ruled out for at least four to six weeks.

Where exactly did the injury occur?

"It was pretty high up. Not high enough to need surgery, but high enough that it's going to take a little bit," he said.

Hart was batting .209 with a .295 on-base percentage, .353 slugging percentage, five home runs and 17 RBIs in 37 games.

He missed all of last season when he underwent microfracture surgeries to both knees. The 32-year-old said he'll at least have the benefit of understanding what it takes to return to action.

"Not that it's a fun thing, but I'm going to try to stay positive and motivate these guys as much as I can and be ready when it's there," he said.

Morrison set for rehab work at Triple-A Tacoma

SEATTLE -- Outfielder/designated hitter Logan Morrison, who has been on the 15-day disabled list with a strained right hamstring since mid-April, will begin his rehab assignment with Triple-A Tacoma on Friday, manager Lloyd McClendon confirmed before Thursday's series opener against the Astros.

Morrison said he'll play designated hitter for the Rainiers during his first three rehab games, then transition to first base before hopefully getting called back up to the Major Leagues.

He can't wait to be back.

"Yeah, this rehab thing gets old. It's no fun watching these guys go out and grind every day, and I want to help contribute somehow," Morrison said. "I feel like when I'm in the lineup we're a better team, whether it shows in the box score or not. I just want to be out there helping the team win."

In eight games this season, Morrison was 3-for-20 (.150 batting average) and didn't record an extra-base hit or an RBI but scored two runs.

Morrison said he shortened his stride while rehabbing to help take pressure off his hamstring. He aggravated the injury while running the bases April 29, but has a good chance of rejoining the Mariners during their season-high 11-game homestand.

"Hopefully if things are going good in the first three games, I can say 'Hey, I feel good, let's go,'" Morrison said. "How realistic it is, I don't know. We'll see."

Worth noting

• Entering Thursday, second baseman Robinson Cano had reached base in 28 consecutive games, marking the longest streak of his career and the longest active streak in the Majors. In his last eight games, Cano owns six multi-hit games and is batting .469 (15-for-32) with five doubles, a home run and eight RBIs.

• Left-hander James Paxton (lat strain) played catch Thursday and is scheduled to make his first rehab start with Triple-A Tacoma on Saturday. Paxton hasn't pitched since April 8 and went 2-0 with a 2.25 ERA in two starts before the injury.

• Right-hander Taijuan Walker (shoulder impingement) will throw a three-inning simulated game Friday where he'll be limited to about 50 pitches, manager Lloyd McClendon said. After that, the club will decide whether he's ready for a rehab assignment.

Adam Lewis is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.