The Barcelona boss believes the Argentine is still recovering his best form and fitness following injury and claims his side encourage criticism due to their high standards
The Argentine went without a goal in four games for the Catalans before scoring twice in the 3-1 Champions League win over AC Milan.
And his compatriot maintains that the 26-year-old needs time to rediscover his best form consistently.
"We've just spoken about Jordi Alba; when he plays his first game [back from injury] his form won't be that great. Leo suffered two injuries that set him back and now he’s striving for excellence," Martino told a press conference.
"Leo is very unpredictable. Last week, after the Madrid game, when I was asked about the situation with Messi, he put in a brilliant performance three days later. Anything can happen with him."
Martino also paid tribute to the attacking understanding between Messi and Cesc Fabregas, saying it is only natural to see them work well together given their time in La Masia.
"They’ve played together since they were kids. Players that have played alongside each other since they were 14 are logically going to be able to carry that on in the first division.
"My feeling is that all players that play well together also get on well. Cesc and Messi have a better understanding beause they've played together for so long."
Barcelona continue to attract criticism for their performances this season but Martino believes the high standards of his side ensure they will always be heavily scrutinised.
"I think that the Barcelona institution, team and squad always encourage this because they have reached excellence. In many cases it's not just about winning a game, it's about winning and playing well," he continued.
"At the moment we're at a stage that is acceptable but there is room for improvement. Sometimes for us winning is enough, and we don't have to put ourselves in one extreme or the other. It's not all bad and the result doesn't mean we don't criticise ourselves to improve from one game to the next.
"First off, we must beat Betis because it calms things down. However, I dont feel that the situation is going to change because we win or lose. For me that will be throughout the whole season. I don't expect it will change because Barca encourage debate."