Brandon Maurer will be on a pitch count against the Marlins.

MIAMI -- Right-hander Brandon Maurer will start Sunday's series finale at Marlins Park, Mariners manager Lloyd McClendon announced on Friday afternoon.

Maurer will fill in for James Paxton, who went on the disabled list April 9 with an oblique injury. His replacement, Blake Beavan, pitched four innings on Tuesday and then landed on the DL with a sore shoulder.

Top prospect Taijuan Walker could've made the start had he not developed shoulder issues as well. Walker was shut down during a rehab start on Tuesday with tightness. The only other pitcher at Triple-A Tacoma on the 40-man roster is Anthony Fernandez, who pitched on Wednesday.

Asked whether Maurer was getting the nod because there weren't any other options, McClendon didn't think so.

"I think he's probably deserving," McClendon said. "He was in consideration during Spring Training to make this club. I think he deserves the opportunity."

The 23-year-old went 5-8 with a 6.30 ERA in 22 games (14 starts) in 2013, his first season in the big leagues.

Maurer has posted a 0-0 record and a 2.16 ERA in four outings (one start) for Tacoma. He is rebuilding his arm strength after a back injury limited him during the spring. Maurer has pitched just 8 1/3 innings.

"I think he's on a pitch count," McClendon said. "I don't want to say what it is. I don't want the opposition to know what it is, but he's like anybody else. We need to watch what he does out here."

Iwakuma pleased after passing another test

Outlook: Budding ace Iwakuma to miss start of '14

MIAMI -- An ailing Mariners starting rotation got one step closer to regaining an All-Star on Friday afternoon.

Hisashi Iwakuma threw a simulated game of 35 pitches to live batters for the first time, and the right-hander included everything from his repertoire.

"I was going 100 percent, just like a game, and I had no pain," Iwakuma said through translator Antony Suzuki. "I was pain-free with my finger. Everything looks good so far."

Iwakuma, who missed all spring with a sprained tendon in his right middle finger, had previously thrown three bullpen sessions. The next step in his recovery will be another 'pen session on Sunday. If that goes well, he will likely pitch his first rehab-assignment game on Tuesday with Triple-A Tacoma.

The hope is Iwakuma will return to the big club after two or three rehab starts by early May. Mariners manager Lloyd McClendon expects Iwakuma to throw around 90 pitches upon his return because of his efficiency.

"We just want to see him continue to progress and stay healthy, and we'll figure it as we move forward," McClendon said. "The main thing is when he comes back, we have to make sure he's ready to compete at the Major League level with all his pitches. It could take 20 innings. It could take less than 20 innings. We'll see."

Pitching coach Rick Waits liked the extension he saw from Iwakuma, as well as how he was "finishing pitches. He passed all the tests for me."

"I think I'm at around 70 percent right now," Iwakuma said. "I still need to command my pitches and get that feel back. It's hard to say right now. I need to have my first rehab start and go from there. [Friday] was good. So that's another step. I have to go one step at a time. That's how I look at it."

After rare game in outfield, Hart starts at first

SEA@TEX: Hart slides, makes tough grab to retire Rios

MIAMI -- Before the Mariners departed for their current two-city, seven-game road trip, Corey Hart packed his first-base and outfield gloves just in case.

That's because Seattle opened a three-game series on Friday night at Marlins Park -- a National League ballpark that negated the use of the designated hitter.

On Thursday against the Rangers, Hart started in the field for the first time this season. It marked his first appearance in the outfield since July 21, 2012, at Cincinnati. Two microfracture knee surgeries kept him out all of last season.

"I wasn't sure about fielding in an American League [game], but I figured here [in Miami]," Hart said. "It was good getting out there. I want to play the field more than not a lot of times. It's been baby steps. Keep me playing and not go backwards with my arms and legs. They've been really patient with me, and hopefully I can continue to progress health-wise so I can stay on the field more."

Mariners manager Lloyd McClendon penciled in Hart, who leads the club with four home runs, as the first baseman Friday. Over nine big league seasons, Hart has played 742 games in right field and 105 at first.

This spring, Hart worked in the outfield and told McClendon he was ready to give it a go after starting as DH in 10 of Seattle's first 14 games.

"It's a couple of things," McClendon said. "Obviously we keep him back in the lineup. I didn't want to put him back in the outfield back-to-back days. We also get a chance to give our first baseman [Justin Smoak] a day off because he hasn't missed a game. We want to make sure he stays strong as well. It's a combination of both things."

Hart hopes he can find his way into the starting lineup at least once more during the series.

"First is fine as long as I can get in there," Hart said. "It's a challenge for me. I like challenges."

Worth noting

• The Mariners played at Marlins Park for the first time on Friday. It is the 47th ballpark the franchise has appeared in during the regular season.