Cahill has attracted a number of suitors after breaking into the England squad.
However he is now putting down roots at Bolton in World Cup year as the club attempt to stave off relegation.
Coyle said: "We have always been focused regarding Gary Cahill. I knew he wasn't going anywhere. That was one of of the stipulations when I came here."
Bolton aim to improve their prospects on Saturday when they face Fulham, who defeated Portsmouth last night.
Coyle said: "What we have to do now is concentrate on the players we have. We need them to play to their maximum and elevate ourselves up the table."
Coyle explained why Portuguese striker Ricardo Vaz Te decided to stay at Bolton and not move to Hamilton on loan.
"It was an opportunity for him to go and play at a good level but he felt it was a bit rushed with it being transfer deadline day, " said the Bolton boss.
"Ricardo said he did not have enough time to think things through. He decided to stay put and that is fine by me."