Michael Higdon cancelled out Rocco Quinn's superb opener for County and Nicky Law then fired the hosts ahead, but Quinn added a second to level the score with 20 minutes remaining.
Both sides went in search of a late winner and it was Keith Lasley who struck to earn Well their first victory at Fir Park since the beginning of September.
"I thought in the first-half we played some very good stuff and didn't take the chances we created," said McCall.
"The second goal was a great lift, but then for some reason we stopped playing - I'm not sure if was anxiety as we hadn't won at home for a while.
"It was a big three points for us, especially with the big cup replay against Aberdeen on Tuesday."
McCall hailed deputy goalkeeper Lee Hollis after his late save preserved the points, but admitted he is likely to make way for Darren Randolph in Tuesday's William Hill Scottish Cup replay with Aberdeen.
"It would have been cruel as we have lost late goals already this season," McCall said.
"I have said to the lads that if they come in for four or five games and play well they will stay in the team, however, if you come in for one or two games then and replace someone who is playing well then it's likely I will take you back out.
"We gave Lee a new contract in the summer and that was on the basis of his performances in training and in reserve matches.
"I would have thought Randolph will be back in goal on Tuesday, but Lee has shown he is a ready made replacement should Darren move elsewhere at any stage."