The Irish defender, recently named Everton's Player of the Season, scored six times in the Premier League from right-back this term.
The international team-mates worked in unison, with McCarthy covering when Coleman ventured forward, to devastating effect.
And Coleman admitted that, without the former Wigan midfielder, his role would certainly not have produced such impressive results.
"Obviously you learn the more you play - you never stop learning," Coleman told the Liverpool Echo.
"I feel comfortable in the right-back position now and thankfully I have got James in midfield who, when I do bomb on, covers brilliantly for me.
"Without him I probably wouldn't have been doing as many forward runs in games as I have done because I can trust him to cover for me. He has been brilliant doing that all season."
The former Sligo Rovers defender also revealed it is not only his attacking play which has improved, believing his defensive work to be more error-free than last season.
"Last season, earlier on I probably made a couple of mistakes but there are not many players who go through a Premier League season without making mistakes," he added.
"It's actually part of my game that I enjoy doing.
"I know a lot of people see me attacking but I get great satisfaction in going one-on-one with a winger and coming out on top.
"Hibbo and Bainesy have helped me a lot and definitely I have improved and picked up pieces from them."