Mike Olt was acquired in July, along with CJ Edwards, Justin Grimm and a player to be named later (Neil Ramirez), for Matt Garza. Olt was having a horrible season and there were vision concerns at the time of the trade. I seem to recall it being better or even all fixed at the time of the trade, but then we got word that his vision troubles continued. Now it's all fixed again, so make of it what you will.
For me, time will tell. Mike Olt wouldn't be the first good prospect with a very high strikeout rate to whiff in AAA and never make much of himself at the MLB level. A year earlier Cubs fans witnessed the same thing with Brett Jackson and the two compare very well to one another. MLB is hard enough, but when you're only putting 65-70% of the balls in play, it gets very difficult to keep a job.
The Cubs don't have a lot at 3rd base that would be in Olt's way and he definitely wants to win the job. Luis Valbuena was the primary 3rd baseman in 2013 and while he got off to a good start, his numbers came back to Earth later on. He finished the season with a 95 wRC+, which isn't much for a 3rd baseman, but for the second year in a row he was very good defensively. His UZR in 2012 was 13.3 at 3rd and it was 8.3 this season.
The end result for Valbuena has been a productive Cubs career. He was worth 1.4 fWAR in 303 PA in 2012 and was worth 2.0 this year in 391 PA. That's 694 plate appearances, or a full season, and he's been worth 3.4 fWAR.
Fangraphs is much more friendly to Valbuena. His WARP over two years with the Cubs is just 0.8 and his rWAR 2.1. Regardless of which you prefer, or just average them and be done with it, he's only been paid $1.4 million over those two years. He's been productive and while not a great hitter, he's made up for it defensively.
Interestingly, he has reverse splits over his career, but has been worse against lefties the last two. The career numbers are more telling though he has only 216 PA vs lefties. We should still expect he'd be better vs. righties. I'd be fine with him not even playing against lefties.
Mike Olt mike make a good platoon partner with Valbuena. Olt has crushed left-handers in the minor leagues, but has only been decent against righties. Olt is also supposedly a good fielder so you'd not lose anything defensively.
I have a hard time believing this front office would just hand the job over to Olt after the disastrous season he had in 2013. They've got a decent 3rd baseman in Valbuena so my guess is that the Cubs would like to see what Olt can do at AAA before calling him up. He does have 1 or 2 options remaining so I expect the Cubs to use it.
Or they could trade him this offseason. We've assumed for some time that Javier Baez will slot over to 3rd when he gets to the big league level, which could be relatively soon. The front office has said that Baez will begin next season at AAA and if they want to get him used to 3rd before a call-up, I could see him starting the year there. That would leave no opening for Olt and the Cubs are definitely not going to hold Baez back in favor of Olt.
Not far behind Olt is Kris Bryant who plays 3rd. They also won't hold Bryant up to keep Olt at a certain position.
Of course, Olt's value is at an all-time low. That would suggest it's not the time to trade him, but he's got talent and several teams would undoubtedly like to acquire him.
For what little it's worth, I think Baez remains at shortstop at Iowa and Mike Olt plays alongside him. Kris Bryant starts the season at AA Tennessee.