The Barcelona boss says the forward will quickly rediscover his scoring touch and has defended supporters of the club following a low attendance at Camp Nou on Wednesday.
The Argentina star has only scored once since the end of October and was denied again in the Blaugrana's 2-0 win over Real Sociedad on Wednesday, despite hitting the woodwork with a free kick.
Martino, however, maintains he was happy with the way the 26-year-old created chances during the match and is fully confident he will soon recapture his lethal touch in front of goal.
"It doesn't worry me that Messi isn't scoring goals," he told reporters after the match. "He had three clear chances today, he'll soon be back among the goals."
Martino went on to admit he was concerned there could be an effect on the team following their defeat to Valencia at the weekend, adding: "We were concerned with the hangover of Valencia. When I thought we might find more space we lost our speed.
"It seemed to me that, except at the start, the team was fluid. We scored two goals as a result of incidents rather than our own play. It was the correct response but the setbacks against Valencia made us think at certain points."
Martino also defended supporters after a low attendance for the Camp Nou meeting, and stressed he would not yet be tempted to look ahead to a possible final against Real Madrid, who won their first leg 3-0 against Atletico Madrid.
"I'm not condoning anything, but if I were a Barcelona fan and I had to work on Thursday, I wouldn't come," he added. "I'm very cautious about being somewhere I'm not. We have to go to San Sebastian and a few years ago Barca suffered there. We have to keep working."