Johnsen failed to clear a long ball out of defence in the dying minutes and substitute Kevin Davies struck an equaliser for the Saints to deny Villa their second away win of the season.
"It was rather sickening to lose the lead with almost the last kick of the game," said Taylor after the 2-2 draw at St. Mary's.
"It was Ronny Johnsen's only mistake of the game. I didn't expect him to do that and we found the ball in the back of our net.
"But you've got to take responsibility at both ends and just before half-time, Darius almost had an open goal and hit the post.
"I felt we should have been away from Southampton by half-time. One suspected Southampton would pick their game up and they did that. They pummelled us after the break and we couldn't get out of our own half."
SOUTHAMPTON MATCH REPORT