Crusaders’ 14-match unbeaten record in all competitions looked under threat when Ballymena striker Shevlin ran on to Jonny McMurray’s nicely-weighted through ball to give the visitors a 17th-minute lead at Seaview.
But skipper Coates headed the equaliser before half-time and Whyte netted a 60th-minute penalty after a foul on Paul Heatley.
“We have been behind I think against Warrenpoint Town, Glenavon and now Ballymena United said Crusaders assistant manager Jeff Spiers.
“It’s a massive, massive win, we’ve really dug in.
“But that’s the way it is going to be until the end of the season as you are coming up against good teams every time.
“Ballymena put us under pressure with big balls into the penalty area to make it hard but we stood tall.
“They are strong but a good team with good players.
“We responded well at 1-0 down and, unfortunately, we seem to waken up at a goal down of late.
“But we didn’t panic at 1-0 down and got the goal back before half-time then Gavin scored the winner.
“Sean O’Neill produced two fantastic saves and that is what you need, everyone playing to their best.
“It has been hectic over the past few months but at the end of Christmas teams will be out in front and, hopefully, we will be there.
“Paul Heatley has had a wee groin injury so didn’t do much in training and then tweaked it tonight.
“Hopefully, we got him off early enough and he is going to get the ice on towards being okay for Tuesday.
“It’s going to be another tough, tough game on Boxing Day, a north Belfast derby.
“Colin Coates is suspended and Rodney Brown out along with a few injuries and others missing.
“But we will give it a look over the next few days to see who is fit. I think it makes our run even more impressive when you consider we went down to Glenavon, for example, last week with six players out.”
“We had Sean Ward stepping into midfield and he was fantastic then but picked up an ankle injury, with Jordan Forsythe stepping in tonight.
“Every week there seems to be something else.”