The young striker tried an audacious backheel in a pre-season friendly which angered boss Roberto Mancini, but the LA Galaxy star believes the Italian thought he was offside
The Italian was clean through on goal before he spun to try an audacious finish, only to see his effort go wide, and he was subsequently hauled off by Mancini.
But Beckham believes Balotelli thought he was offside and has urged the former Inter man to be more professional in future.
The former England captain told BBC Sport: "I've watched it back and, from his mannerisms, I believe he thought he was offside.
"Mario's been a great player for quite a few years and is still very young.
"He'll continue to get better I am sure.
"But it doesn't matter whether you think it was offside or not. There are a lot of young kids watching these teams and great players who come out here. You have to be professional and score the goal."
Mancini insisted that Balotelli knew he was not offside when he sluggishly kicked the ball wide, and said the youngster knows he has made a mistake.
"In football you always need to be professional, always serious and in this moment he wasn't professional," Mancini said.
"Mario needs to understand his behaviour has to be good in every game - not just in a final or a semi-final but every game.
"He knows he made a mistake. Football should always be serious and if you have a chance to score, you should score.
"Mario is young, I want to help him. That's the end of it. To take him off after 30 minutes of the [friendly] game is enough punishment. It will not have been easy for him - but it has to be a lesson."