Gallas left Davies in a heap on the ground in the build-up to Arsenal's 52nd minute equaliser, which levelled the scores at 2-2 before Arsenal went on to win the match 4-2 to go top of the Premier League.
Davies was forced to leave the field at the Emirates Stadium and Coyle, whose two matches in charge of Bolton have both ended in defeats to Arsenal, was left fuming.
"I think it was closer to an assault than a tackle, and for a foul not to be given ... I felt he went over the ball," Coyle told reporters.
"He (Gallas) certainly hasn't touched the ball, and my lad has got suspected serious ankle damage.
"There is no doubt it was a free-kick and I would suggest it was closer to a sending off as far as I am concerned.
"Having said that I recognise we can defend better than what we did late on, but that was the big turning point of the game."
Arsenal manager Arsene Wenger was apologetic.
"If the tackle was a bad one then I apologise," Wenger told reporters, adding his players did not kick the ball out of play because they did not realise Davies was so badly injured.
Wenger had, however, earlier defended the tackle.
"They can complain, but it didn't look to me from outside that it was very bad," he told Sky Sports. "I can show you some tackles if you want.
"Put them all together from the two games -- their tackles and our tackles and then we can compare."
NEWS: Arsenal recover to take top spot
