Blackburn claimed a fortunate point in the 0-0 home draw with local rivals Everton.
Rovers struggled throughout the game and their only chances came at the beginning of the match and late on, both falling to Roque Santa Cruz.
Blackburn boss Mark Hughes was equally baffled with the offside decision even if his side got the benefit of the doubt in this instance.
"Do you understand the rule these days?" Hughes asked the assembled press.
"First phase, second phase, is he active, isn't he active? I've had this argument before and it's too much of a grey area.
"It's difficult for officials and frustrating for managers.
"Initially he (Johnson) was offside in the first phase although David (Moyes) will argue he wasn't in the second. It's crazy really.
As to the match itself, "I thought it was decent game with two clubs determined to get something for European qualification.
"It's disappointing as the home side not to take three points but maybe at the end of the season we will see this as decent point.
"It keeps our run going of seven unbeaten games which is a good return."