Martino admitted it was a match the Catalans just needed to get out of the way, with the second leg of their Champions League quarter-final against Atletico Madrid looming on Wednesday.
Two goals from Lionel Messi and an own goal from Jordi Figueras secured the win, with Ruben Castro on target for the visitors, but Barca never looked totally comfortable.
"In a sense I was expecting the match to not play out like our previous ones. For once, I'm going to focus 100 per cent on the result, not how we played," Martino said on the club website.
"I don't want to make excuses. The feeling that I have is that, in between the game (against Atletico) this past Tuesday and the one next Wednesday, this match against Betis snuck up on us. We needed to win in order to continue putting pressure on the leaders."
The win kept Barca in second place, one point behind Atletico.
"I wanted to rest some of the players ahead of Wednesday's game against Atletico if the game had gone differently. It didn't play out that way," Martino added.
"I probably could have given more rest to some of the players who featured on Tuesday. Perhaps I didn't go far enough with the rotation."
Barca are enduring a tough time off the pitch after being hit with a FIFA-imposed transfer ban last week, but defender Marc Bartra said the mood in the camp was still high ahead of the return match with Atletico. The first leg at the Nou Camp finished 1-1.
"I'm very optimistic. We'll go all out at the (Vicente) Calderon with the hope of going through to the next round," he said.