They made the moves this afternoon to get them down to 75, and they actually did so without cutting anybody. The Colts placed running back Vick Ballard, tackle Ulrick John, and running back Deji Karim on injured reserve and placed fullback Stanley Havili on the reserve/physically unable to play list.
Ballard was injured near the start of camp and it was confirmed that he would miss the season with a torn achilles. We've known for a while that he was heading to IR, so why the long wait? Simply put, the Colts wanted to wait to IR him until they could do so without waiving him first. The Colts thought there was a good chance of someone claiming him and they didn't want to risk it.
The same is true of Ulrick John. He was injured in the first preseason game, but the Colts also waited to place him on IR until they could do so without waiving him. To me, that's very interesting. I don't think another team would have claimed John, and I didn't think he was important enough to the Colts' management for them to hesitate placing him on IR, but obviously the Colts thought there was a chance he would be claimed and they value him enough to wait to place him on IR. I find that very interesting.
Deji Karim was just recently signed by the Colts, and he was inactive against the Saints for his first game. I don't even know how much he practiced with the team, but his return to the Colts was very short lived - he's on IR about a little over a week after being signed.
As for Stanley Havili, he was placed on the PUP list at the start of training camp and hasn't practiced since. That means the Colts currently have only one fullback on their roster, as they released Cameron White yesterday, and it's Mario Harvey, who has underwhelmed in preseason. The Colts options are to either go with Harvey, go without a fullback, or sign another fullback. To me, the most likely option is the first one, but we'll see. Havili would be the best option once he's back, but he won't return until at least week seven. That's when he can begin practicing with the team, and then after that point they have three weeks to either activate him or place him on season-ending IR.