The coach has stressed that there's no guarantee the attackers will form a dangerous duo and has warned his men not to underestimate Man City.
The Argentina international and his Brazilian counterpart impressed earlier this campaign, but they have been unable to make much of an impact together recently - partially because of a string of fitness problems.
"Messi and Neymar haven’t played much together this season because of injuries. The times they have played together, they have linked up well, but recently they haven’t had much connection on the pitch," Martino said at a news conference. "You can’t guarantee they will always be synchronized just because it’s the best player in the world and the next best player in the world."
The Barca coach then turned to the second leg of the Champions League round of 16 tie against Manchester City and warned his men not to take things lightly after their 2-0 away win in the first leg.
"Tomorrow I think Manchester City will make changes to the team. Sergio Aguero is very dangerous but they have many other players who are just as worrying," the Barca boss said. "We have to think that 10 or 12 days ago, we played a very good match against Manchester City. I don’t see why we can’t do the same tomorrow, and I am sure we will play well.
"We have to separate the league from the Champions League and we are at an advantage for tomorrow."
Barca comes into the clash at Camp Nou on the back of a 1-0 defeat at Valladolid on Saturday.