ST. LOUIS -- In terms of their big picture, the Marlins are aiming to make improvements any way possible. So when they saw an opportunity for a potential upgrade in the outfield, they decided to make a move.

On Wednesday afternoon, the Marlins acquired outfielder César Puello from the Angels for cash considerations. In corresponding moves, Miami designated for assignment Rosell Herrera, who is out of options, and also placed right-hander Pablo López (right shoulder strain) on the 10-day injury list.

"With Cesar, it's a situation for us to ask, 'How do we get incrementally better?'" Marlins manager Don Mattingly said. "We felt like this opportunity came up with what happened in Anaheim and their roster. We were able to rethink it a little bit better."

Puello, who was DFA'd by the Angels on Monday, was in his native Dominican Republic when the trade was announced. He was able to make it to Busch Stadium in time for Wednesday night's game against the Cardinals.

In recent years with the Angels, Puello played for Miami's Triple-A New Orleans manager, Keith Johnson, who previously worked for Los Angeles.

"It sounds like he's a kid who plays extremely hard," Mattingly said. "He's having a good year."

Puello appeared in 12 games for Los Angeles, batting .390/.500/.683 with three home runs and 12 RBIs. He is a right-handed hitter who plays mostly left and right field. The Marlins plan to use him also in center field, if necessary.

At Triple-A Salt Lake this season, Puello had a slash line of .299/.434/.507 with seven home runs and 27 RBIs.

Lopez is 5-5 with a 4.23 ERA in 14 starts. In 76 2/3 innings, he has 73 strikeouts and a WHIP of 1.12. The right-hander last pitched on Saturday, allowing three runs on seven hits in seven innings in a win over the Pirates.

Last September, Lopez missed the final month of the season due to a right shoulder strain.

Lopez is the third starter from Miami's Opening Day rotation to be placed on the injured list. He joins Jose Urena (herniated disk) and Caleb Smith (left hip inflammation). Urena is on the 60-day IL, and Smith is on the 10-day IL. Elieser Hernandez and Jordan Yamamoto have filled their spots.

Prospect Zac Gallen is being called up from New Orleans, and will be added to the 40-man roster and start against the Cardinals on Thursday.

"It's been a little testing period for us, but so far, obviously, the kids have come up and are throwing the ball really well," Mattingly said. "It tests our pitching depth. It's what we consider the strength right now in the organization.

"It's going to be good to look at some more guys, obviously, at the expense of guys hurt. You don't want guys hurt, but it gives guys an opportunity to show what they can do."