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5/3/2014 5:28 P.M. ET

Cubs place Sweeney on DL, call up Coghlan

CHICAGO -- Ryan Sweeney made a great catch Friday, but the Cubs outfielder strained his right hamstring on the play. On Saturday, he was placed on the 15-day disabled list.

Sweeney has a moderate strain of his right hamstring, and will be sidelined at least three weeks, manager Rick Renteria said. Sweeney was batting .200 (11-for-55) with two doubles and six RBIs in 20 games.

"It's not as bad as we thought, but he's definitely on the DL," Renteria said.

Sweeney came up limping after chasing down Allen Craig's fly ball in the Cardinals' eighth inning. Sweeney caught the ball, but couldn't make the throw home and flipped it to left fielder Ryan Kalish.

The Cubs selected the contract of outfielder Chris Coghlan from Triple-A Iowa to take Sweeney's spot. Coghlan, 28, was in camp as a non-roster invitee, and played in 24 Cactus League games before he was assigned to Iowa in the final days.

A left-handed hitter, he was batting .243 (17-for-70) with five doubles, six RBIs, six stolen bases, 13 walks and a .379 on-base percentage in 24 games with Iowa this year.

"Any time you're in Triple-A, it was humbling," said Coghlan, the 2009 National League Rookie of the Year. "It's a grind. I'm grateful for the opportunity to play every day and get back here."

A career .270 big league hitter, Coghlan was limited to 70 games with the Marlins last year because of a right calf injury, and batted .256 (50-for-195).

"He's a guy we can use off the bench, he's a guy who can start in the outfield," Renteria said of Coghlan. "He just continues to give us a little flexibility."

Coghlan's plan was to make the Cubs' Opening Day roster.

"There's no guarantees, but that's this industry," he said. "There's no guarantees no matter what. You have to prove yourself every day. I came with the expectation that I was going to make the team and be on the team. That's what I expected out of camp. It didn't work out, and I'm here now, so I'm grateful."

He got some advice from former Cubs outfielder and Hall of Famer Andre Dawson, now with the Marlins' front office, who recommended Coghlan play for the Cubs. They have yet to exchange text messages.

Coghlan was happy to see sunshine at Wrigley Field on Saturday. The Iowa team has had a lot of games postponed because of the weather.

"I'm sure you dealt with the same thing," he said. "It's just the way it is in the Midwest. You get through that first month, and the sun comes out, then you can do some damage."

Rosscup optioned as Cubs activate Arrieta

CHICAGO -- Cubs pitcher Jake Arrieta was activated from the disabled list in time to start Saturday's game against the Cardinals and lefty Zac Rosscup was optioned to Triple-A Iowa.

Arrieta reported to Spring Training with tightness in his right shoulder. Acquired last July from the Orioles in the Scott Feldman deal, Arrieta, 28, made five Minor League rehab starts, and was 1-1 with a 2.25 ERA with Class A Daytona and Double-A Tennessee.

The Cubs will continue to carry 13 pitchers, and manager Rick Renteria said that's OK.

"We have [Carlos Villanueva] who gives us a swing position, and based on everybody we're using it gives us flexibility and we have to be able to protect guys," Renteria said. "It works."

Rosscup has appeared in two games in two different stints with the Cubs. In his last outing Tuesday against the Reds, he walked one in one inning. The Cubs still have two left-handers in the bullpen in Wesley Wright and James Russell.

Renteria staying course with 'fluid' closer situation

CHICAGO -- Hector Rondon picked up his third save of the season on Saturday, but Cubs manager Rick Renteria wasn't ready to crown the right-hander as the closer.

"Rondon has been used in that particular situation but it's still fluid," Renteria said before Saturday's game. "It'll depend on where we're at as to who we use in those innings."

On Saturday, Rondon entered in the ninth with a 3-0 lead against the Cardinals. Yadier Molina and Jhonny Peralta both singled, but Jon Jay hit a comebacker to start a 1-6-3 double play, then struck out Mark Ellis to end the game.

If the situation was "fluid" before the game, what is it now?

"It's organic still, as they say," Renteria said.

The Cubs have been trying to find the right combination since removing Jose Veras as the closer on April 11 after he blew a two-run lead against the Cardinals. Rondon finished that game for his first save. He notched his second on Friday in a 6-5 win over St. Louis.

Rondon has come a long way. The right-hander was the Cubs' Rule 5 Draft pick in December 2012.

"It feels amazing right now," he said. "Everything I've been working for last year, everything is coming together this year. It's good for me."

The Cubs' other options at closer include Pedro Strop and Justin Grimm. Veras is on the disabled list with a strained oblique and was to begin a rehab assignment soon. In the meantime, Rondon will be ready.

"I need to be more aggressive," Rondon said. "I need to make my first pitch for strikes. That's big for me."

Does he get nervous entering a game with a one-run lead?

"Sometimes in the bullpen, everybody has nerves, but when we go to the mound, everything goes away," he said.

What was the key Saturday?

"I knew I needed to make a good pitch," Rondon said.

"That inning is not for everybody," Cubs catcher Welington Castillo said of the ninth. "[Rondon] made his pitch. It's all him."

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.