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06/09/12 11:16 PM ET

Rosario makes strong impression in 2012 debut

MIAMI -- In spite of an 8-2 loss Friday night that saw the Marlins drop their fourth straight game, manager Ozzie Guillen had at least one positive to take away from the night: the performance of reliever Sandy Rosario.

Rosario, who was called up from Triple-A New Orleans on Friday, made just his seventh career appearance, and his first since Sept. 25 against the Brewers. The 26-year-old right-hander entered the game with one out and runners on the corners in the seventh and proceeded to pitch 1 2/3 hitless innings of relief.

"Rosario did a tremendous job," Guillen said. "Great job by him."

Rosario induced an inning-ending double play against the first batter he faced, and then got through the eighth, allowing only one runner to reach -- on an error by Omar Infante. He capped off his outing by striking out Desmond Jennings.

What Guillen was most impressed with about Rosario, however, was his velocity. The righty touched 97 mph on the radar gun and his fastball consistently hit 95-96 mph.

"I didn't know this kid would throw that hard. I kind of liked it," Guillen said. "He throws hard, he's got good stuff and he throws strikes. You throw that good, you throw strikes, you're going to be in a good position to repeat."

Rosario struggled in his second appearance, allowing three runs on four hits without retiring a batter in the eighth inning of Saturday's 13-4 loss.

Murphy designated for assignment

MIAMI -- The Marlins designated infielder Donnie Murphy for assignment following the team's 13-4 loss to the Rays on Saturday night.

Murphy went 0-for-1 after entering the game as a pinch-runner for Hanley Ramirez in the sixth inning. Murphy hit .133 (6-for-45) in 25 games this season, including eight starts at second base.

The team plans to make a corresponding roster move Sunday morning, and a likely candidate to rejoin the team is first baseman Gaby Sanchez, who was optioned to Triple-A New Orleans on May 19.

Sanchez was hitting .197 at the time of his demotion, but has used his time in the Minors to get back on track at the plate. Sanchez was out of the Zephyrs' lineup Saturday night, but went 4-for-4 with a home run, four RBIs and three runs scored on Friday night.

Since being optioned, Sanchez has hit .310 with a .494 on-base percentage in 19 games.

Morrison expected to be in lineup Sunday

MIAMI -- After a couple days to clear his mind of his struggles at the plate, Logan Morrison is expected to be back in the lineup for Sunday's series finale against the Rays.

"He'll be back. We need this kid," Marlins manager Ozzie Guillen said. "Hopefully, mentally [the two days off] helped him. ... This kid has struggled this month and last month, and we need him to get back on track. We're a better ballclub when he's in the lineup."

Morrison is in the midst of a 0-for-18 skid at the plate and is just 3-for-25 (.120) in June as his season average has plummeted to .214. In May, he hit .176 with one home run and 19 strikeouts -- not the type of production the Marlins hoped for from the batter who is supposed to provide protection in the lineup behind slugger Giancarlo Stanton.

Part of Morrison's struggles, he said, have been slight mechanical issues with his swing, but he has also been chasing pitches and as a result, most of his issues have been mental.

"You're only as good as the pitch you swing at, so I got to do a better job of swinging at strikes," Morrison said.

Morrison, who has shown a positive attitude about taking time off, has been working in the batting cages on correcting his swing and getting back to what got him to the Majors in the first place.

Morrison is not the only Marlins player to go through struggles offensively this season. First baseman Gaby Sanchez was demoted to New Orleans on May 19 when his average dipped to .197, and catcher John Buck is currently hitting .167.

"Everybody goes through it ... but nobody's going to get you out of it but yourself," Morrison said. "That's all you need is yourself to get out of it and know that you were successful once being in the big leagues and you can do it again. It's not like you forget how to do those kind of things."

Kearns' hamstring not yet 100 percent

MIAMI -- Austin Kearns may be back from the disabled list, but if you ask Marlins manager Ozzie Guillen, Kearns' right hamstring isn't completely healed just yet.

"To be honest with you, I don't think he was 100 percent," Guillen said. "You're never 100 percent, but I think he looked a little slow. We'll see, it's going to take time, it was his first game back."

Kearns started in left field Friday night, and at times it looked like his hamstring may still be sore, including the third inning, when the Rays' Matt Joyce hit a blooper to shallow left off that turned into a double when Kearns was slow to get to the ball.

Guillen said Friday he would be cautious as he eased Kearns back into action, and the Marlins' skipper didn't plan on playing him in left field on consecutive days because of the hamstring, which caused Kearns to hit the 15-day DL on May 24. Guillen stayed true to his word Saturday, starting Donovan Solano in left for the third time this season.

Kearns was still in the lineup, though, starting at first while Logan Morrison sat out another day as part of a short mental break to help clear his mind of his struggles at the plate.

By once again sitting Morrison, moving Kearns to first and putting Solano in left and Justin Ruggiano in center field, the Marlins had seven right-handed hitters and two switch-hitters -- Jose Reyes and starting pitcher Carlos Zambrano -- in the lineup against Rays lefty Matt Moore.

Kearns went 1-for-4 in Saturday's 13-4 loss.

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