MIAMI -

The Miami Marlins started Monday just one game out of first place in the National League East, and they decided to go for it, making eight roster moves -- and that does not count signing a player who could be their ace of the future.

The Marlins called up left-hander Andrew Heaney and right-hander Anthony DeSclafani from Triple-A New Orleans on Monday and have plugged both pitchers into this week's rotation.

Heaney, the team's top prospect, will make his big-league debut on Thursday against the New York Mets. The 23-year-old was the ninth overall pick in the 2012 draft and had a combined record of 7-2 in the minors this season with ERAs of 2.35 in Double-A and 2.74 in Triple-A.

He will try to shore up a rotation that was rocked last month by the loss of ace right-hander Jose Fernandez to season-ending elbow surgery.

"It's surreal," Heaney said of getting the call. "You think of how it might happen, and then it does, and it doesn't hit you until now when I'm in the park and looking out."

DeSclafani, 24, who made his big-league debut earlier this season and went 1-1 with a 5.56 ERA in two starts, will start again on Tuesday against the Chicago Cubs.

To make roster room for their two new starters, the Marlins designated for assignment left-hander Randy Wolf, 37, and right-hander Kevin Slowey, 30. Wolf, trying to make a comeback from a second Tommy John surgery, went 1-3 with a 5.28 ERA. Slowey, with 17 appearances, including 15 in relief, was 1-1 with a 5.30 ERA.

Right-hander Jacob Turner, who had been set to start on Tuesday, will now pitch out of the bullpen, and he took the loss in that role Monday night. The Cubs scored on him in the 13th inning to come away with a 5-4 win.

Left fielder Christian Yelich, who had missed the past two games due to a strained lower back, was replaced by outfielder Jake Marisnick, who was also called up from New Orleans. Marisnick started Monday night in center field for the Marlins, who moved Marcell Ozuna, at least temporarily, to left field.

Marisnick got off to a great start on Monday, batting leadoff and singling, stealing a base and later scoring in the first inning.

"Jake's natural position is center," Marlins manager Mike Redmond said. "I feel confident he can play anywhere. But I just felt it was easier for Jake as a young guy to come up and play your natural position. He covers a ton of ground.

"I talked to (Ozuna) about it, and he's fine. Wherever he plays, he plays."

Redmond said he did not think Yelich would require longer than the 15 days on the disabled list, retroactive to Saturday.

In the final set of moves, the Marlins optioned utility infielder Donovan Solano to New Orleans and called up first baseman Justin Bour from the same team.

The Marlins have a glut of utility infielders with Ed Lucas and Jeff Baker already on the roster, and that made Solano expendable.

Bour, who struck out as a pinch-hitter on Monday, gives the team a left-handed hitter off the bench, which is something Miami did not have before the move.

Also on Monday, the Marlins announced the signing of the second overall pick in the 2014 draft, right-hander Tyler Kolek, who has routinely thrown over 100 mph.

"We're trying to win," Redmond said. "We felt like bringing the young pitchers in ... this was the time. Hopefully, they will help us win games."