Following England's poor showing at the tournament, there is now likely to be a shake-up of playing personnel and Coyle believes Cahill will be amongst those staking a claim.
'My disappointment was that when the provisional squad was named, he wasn't in that 30, because I believe if he was, Mr Capello and his assistants would have seen him training and realised that this boy can play,' Coyle said.
'He has got pace, he has got a goal-threat - he has got everything, but obviously he never got that opportunity.
'I rang him straight away to make sure he was alright and he was disappointed, but he said "well, I just have to make sure that next year I go and push myself to get into the squad". I thought that was a terrific answer.
'Mentally he is there, as well as physically and ability-wise. There is no doubt for me that he will really push himself into that England squad.'
Tottenham centre-backs Ledley King and Michael Dawson - as a replacement for the injured Rio Ferdinand - were picked for the World Cup, but Coyle feels Cahill is a match for any of his rivals in that position.
'It's difficult to say how much of a difference he would have made,' Coyle said.
'What I would say though - and you have to remember that as his manager, I'm biased - is that England have terrific players, but I feel Gary Cahill is as good a centre-half as we have in this country.
'I'm not being smart after the event - I said this before the World Cup and I have been consistent with it since day one.
'For me, Gary Cahill is the complete package. I accept that he had a terrible injury and was coming back from that, and I think he was watched at one of our games when we played Portsmouth.
'He made a slight mistake in that game and I don't know if that went against him, but what I do know is that within that period, we went to Chelsea and he stood toe-to-toe with Didier Drogba and was outstanding.
'We went to White Hart Lane and he was outstanding again. Michael Dawson and Ledley King played in the game and they are very good players - I'm not suggesting anybody
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