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4/11/2014 11:11 P.M. ET

Rookie Leone contributing to solid bullpen

SEATTLE -- The Mariners' bullpen had combined for an eight-inning scoreless streak over two games entering Friday night's opener against the A's.

Seattle relievers led the American League and were third in MLB with a 1.75 ERA in 25 2/3 innings. In eight games, the bullpen's only major blemish came when Hector Noesi grooved a fastball to A's outfielder Coco Crisp, who smashed it for a 12th-inning walk-off homer April 3 in Oakland.

The next day, Noesi was designated for assignment, and 22-year old reliever Dominic Leone was recalled from Triple-A Tacoma. In two big appearances through Thursday, Leone hadn't given up a run, with two strikeouts and a walk in 2 1/3 innings.

"It was a quick turnaround," Leone said. "The spring was good to me. I was fortunate enough to pitch well and get to bond with these guys and get to know a lot of them. It wasn't awkward. It's not like I didn't know anybody. I was with them about a week ago."

Seattle weighs effect of brief spring on Walker

SEATTLE -- Mariners manager Lloyd McClendon on Friday said he had not named a starting pitcher for Tuesday's game against the Rangers at the Ballpark in Arlington but that a decision should come by the end of Saturday.

Right-hander Taijuan Walker, rated the organization's top prospect by MLB.com, threw five scoreless innings Wednesday in a rehab start for the Double-A Jackson Generals of the Southern League. Walker allowed three hits with 10 strikeouts and a walk while throwing just 85 pitches. It was his second Minor League rehab start.

Before the season, McClendon said he expected Walker to begin the year in the starting rotation. In late February, Walker was sidelined with inflammation in his throwing shoulder that kept him out of Spring Training, but after his latest start he said he was ready rejoin the big league club.

So why the holdup?

"It has nothing to do with his lack of big league experience," McClendon said. "I think it has everything to do with his lack of work in Spring Training and the amount of innings he had because of injury in Spring Training. We have to make sure that if he's the guy we're going to bring, then he's got to be ready to compete at this level and there are no bars or limitations."

McClendon said right-handed pitcher Blake Beavan "threw the ball extremely well" in his latest Minor League start and was "in the mix" to fill the rotation spot vacated when starter James Paxton was placed on the 15-day disabled list (left lat strain) and reliever Lucas Luetge was recalled from Triple-A Tacoma earlier this week.

In two starts with Tacoma, Beavan is 1-0 with a 2.08 ERA with eight strikeouts and four walks in 13 innings.

McClendon said he wanted Walker to be 100 percent before the 21-year-old could be promoted from Double-A. After making his MLB debut late last season, Walker was 1-0 with a 3.60 ERA and 1.000 WHIP over three big league starts.

"The game is a little bit more stressful at this level than at the Minor League level in the number of pitches that you throw," McClendon said. "The outs that you get at this level are harder to get. We have to take all that into account when we decide whether or not we're going to bring him or somebody else. We're still talking about all of that."

McClendon added that Paxton was "seven or eight days" away from being re-evaluated before he could start a rehabilitation program. Paxton was forced to leave Tuesday's home opener in the top of the sixth inning with the injury, though he said he tweaked it after throwing a pitch in the fifth.

Mariners seek to develop Romero vs. lefties

SEATTLE -- Rookie Stefen Romero started in right field while batting seventh on Friday, which has become the norm when Seattle goes against left-handed starters. The Mariners opened their series against the Athletics versus a southpaw in Tommy Milone, who was making his season debut after his scheduled start last week against Seattle was postponed when Oakland's O.co Coliseum received an overnight rainstorm that left the field soggy and unplayable.

Manager Lloyd McClendon said Romero had impressed him during spot starts against left-handed pitching.

"If he gets three, four home runs tonight, he'll be great," McClendon quipped. "He had a great spring; we need right-handed balance in our lineup, and he provides that. I think he's going to be a fine Major League player. He just needs to get his at-bats and get his time out there. This young man can play the game, and I think he'll be an impactful type of player for us this year."

In 2012, Romero was named the organization's Minor League Player of the Year when he hit .352 with 23 home runs, 101 RBI's and 85 runs scored in 116 games between Class A Advanced High Desert and Double-A Jackson. That was as an infielder. Romero's first career appearance in right field came this year in Spring Training.

"Nothing can compare to live reads off the bat," Romero said. "Even BP is not the same because the guy's throwing 45 miles per hour, so especially in a game it's so much faster. The biggest transition is just [learning] game situations."

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