The Blaugrana boss says he has the utmost faith in the Cameroon international, who is set to start in Seville with Sergio Busquets having been given the weekend off
The former Arsenal midfielder is likely to start in place of Sergio Busquets, who is being rested and has not travelled to Andalusia.
Song has found regular first-team opportunities difficult to come by since arriving at Camp Nou in the summer of 2012 but Martino has been impressed with the Cameroon international when he has stepped into the team.
"I have a high opinion of Song,” he told reporters ahead of the match. "In the three or four games he has played, he has always responded with high-quality performances.
"We have looked at ways of him playing him in midfield alongside Busquets when both are available. They were together against Real Madrid and Celta, too.”
The Barca boss says he is expecting a difficult evening despite Betis’ struggles in La Liga so far in this campaign, with Pepe Mel's men currently bottom of the table with just two wins from 12 matches.
Martino added: "They have some great players. Although their league results have not been too good, they are doing well in Europe. We expect a very difficult match, especially with them being at home.
"Betis are dangerous because they are a good team. Their league position doesn’t matter.
"Anyone who saw how they played against Real Madrid in the first match of the season knows they have a good team.
"The next game against Granada is a long way off, so if we don’t win we are going to be under pressure for the next two weeks [because of the international break]. Winning at Betis will give us peace of mind."
As well as Busquets, Gerard Pique is also ruled out for Barcelona. Javier Mascherano is available but looks likely to be rested, meaning Carles Puyol and Marc Bartra could start in the centre of defence.