The Catalan side have only won one of their last four games in the league while Atletico Madrid have moved three points ahead of them on 57, and Real Madrid are now only below them on goal difference.
Last weekend Barca crashed 3-2 at home to Valencia with Messi scoring from the penalty spot, his only goal in the four league matches he has played since returning from a hamstring injury that kept him sidelined for almost two months.
In midweek they beat Real Sociedad 2-0 at home in the first leg of their King's Cup semi-final when Messi, who has sent records tumbling in recent seasons with his scoring feats, again drew a blank.
"In the games with Real and with Valencia, the team had chances to widen the scoreline and it is true that there are a lot of problems with scoring," Martino said.
"I'm not talking about it being difficult to create chances, we have openings but we aren't taking them," Martino told a news conference on Saturday.
"It happened against Levante, Valencia and Real. We create six or seven chances and don't take them."
Martino though refused to point the finger at Messi.
"I don't think it is something to talk about like that. There is too much talk about whether he is playing well or badly," he said.
"He should be left alone for a couple of days. He is the best player in the world and we should just enjoy watching the way he plays."
Neymar has also had a difficult first season at the Camp Nou where he has been unable to reproduce the prolific form that brought him from Brazil. He has missed the last three league games with an ankle injury and will not be ready to face Sevilla.
"All the players that are here have a lot of quality but they need time to adapt. Obviously not the home grown players but those who come from abroad," said Martino.
"Some take three or four months and some a year but there is no doubting his ability. Barcelona is a very big club and it is necessary to have a period of adaption."
Barca face a tough match against Sevilla with Martino concerned about the threat they pose from set pieces.
"I told the players that this is probably one of the most difficult away games that we have left. They are solid, hard working and strong at home," the Argentine said.
"They are very effective at set plays and are possibly the team in the league that scores most goals from them thanks to the delivery from (Ivan) Rakitic but we also need to be wary of them on the counter."
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