The Blues have long been linked with the England defender and recently settled on a fee for the player, believed to be in the region of £5 million.
However, the transfer hit a snag earlier in the week when reports began to surface that both Cahill and the West Londoners had failed to agree personal terms.
But on Friday, Coyle confirmed that the deal was close to completion and admitted that the England international is set to miss the club's FA Cup encounter against Macclesfield Town.
"Gary Cahill will be one of those to miss out on the game, and it's nothing to do with the continuing speculation regarding Chelsea. He's one of a number of players that probably needs to rest given the amount of games they've played," the Trotters manager said.
"And moving on to that, my own opinion is I think there's a chance the deal can be concluded by the end of the week. That's where we're at but I'm not a party to any continued dialogue between Chelsea and Gary's representative.
"They were respectful of the other night, the fact we had a big game against Everton
and that kept Gary focused and he showed his quality by doing that in the game."
