MESA, Ariz. -- With just days left in spring training, Chicago Cubs third base prospect Mike Olt has made the team, as has outfielder Ryan Kalish, the Cubs announced Thursday.

"Olt showed us a lot this spring," general manager Jed Hoyer said. "The way he swung the bat was really impressive. We like the work he's done at third."

In addition, the team announced Carlos Villanueva will be the team's fifth starter and Chris Rusin will be sent to Triple-A.

Olt, 25, was a rising prospect in the Texas Rangers organization but vision problems derailed him last season. The Cubs couldn't get him in a trade in 2012 -- when he was on his way to hitting 28 home runs at Double-A -- so they tried again in 2013 as he was slumping. They nabbed him when they traded Matt Garza to the Rangers in a deal that netted them four prospects, including Olt. The vision problems cleared up and Olt started hitting again.

"Making sure he can play third base, that was really the key once it was clear his bat was ready," Hoyer said. "Over the past two weeks it was pretty clear if he was able to play third base we wanted the bat at Wrigley Field."

Olt battled shoulder problems at the beginning of camp and was unable to play the field other than at first base, and he's been playing there for about a week. He swung the bat well from the beginning of camp and it carried over to games. Going into Thursday's Cactus League finale, Olt was hitting .275 with five home runs and 12 RBIs. The latter statistic is tied for the team lead with Luis Valbuena.

"At some point you just become a believer, and he really hasn't slowed down," Hoyer said.

Manager Rick Renteria wouldn't commit to Olt playing every day at third, as the Cubs have the left-handed-hitting Valbuena, who leads all hitters in baseball this spring with six home runs. But as things play out, Olt will be given every chance to be the long-term starting third baseman.

Kalish was also a rising prospect with the Boston Red Sox organization before injuries set him back. After neck and shoulder problems cleared up, the Cubs invited him to camp and he won a reserve outfield job. He has six stolen bases this spring and has been a spark for the Cubs when in the lineup.

"Great energy and he can play all three outfield positions," Hoyer said.

The 30-year-old Villanueva had a 5.60 ERA in six spring training appearances. The 27-year-old Rusin gave up four home runs in his last spring start Wednesday.

The Associated Press contributed to this report.