The Spain international goalkeeper announced last year that he would not extend his contract beyond the current campaign, instead opting to depart Camp Nou, where he has spent his entire professional career.
And Martino believes that call might have had a negative impact on the team.
"I'm very much surprised by Valdes," Martino told reporters ahead of Sunday's La Liga clash with Levante.
"His decision not to further his contract put the club in trouble because the goalkeeper has a very large impact on the team.
"It's the only position where you know a player won't be there and that means we have to review our choices."
Barcelona are currently level on points with Atletico Madrid at the top of La Liga, three points clear of Real Madrid in third. And Martino thinks it may take more than 100 points to win the title this season.
"We may be looking at a league championship in which 100 points aren't enough," he continued. "It's all about not losing the momentum that the other two leading teams have."
Reigning champions Barca meet Levante on Sunday, a team they beat 7-0 in the reverse fixture, but Martino is not expecting a similar encounter this time around, adding: "I believe that game wasn't typical, especially looking at what Levante have done since then.
"They've proved themselves to be a solid and combative team, fast on the break and good in defence.
"They haven't conceded as many goals against any opponent since then. I don't expect a repeat of that match."
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