Shearer came out of his goal in the third minute to cut-out a long ball from Sam Togwell but slipped on the wet turf which allowed Drew Talbot to cross for Jordan Bowery to side-foot the ball into an empty net.
It was a nightmare start but Rotherham hit back and deservedly drew level in the 51st minute when Kayode Odejayi turned superbly to beat home keeper Tommy Lee with a right-foot drive from just inside the area.
Evans thought his team deserved at least a point and was quick to hand some of the credit to Shearer.
"It was a freak goal but the pleasing thing for me is the big fellow doesn't let his head go down if he makes a mistake," said Evans. "I thought his handling after that was excellent and he made a couple of good blocks at the near post. Those conditions were treacherous for a goalkeeper for 20 minutes of the first half.
"I thought we got the worst possible start but I thought we regrouped and we dominated for spells. If you are going to wilt and think the world's against you it's going to be in the first two minutes but there was one team wanting to go another five minutes and that was us."