Two goals from Lionel Messi either side of half-time and an own goal from Jordi Figueras secured victory for the champions, with Ruben Castro responding for the visitors in a less-than-straightforward afternoon for the home side.
The win means that Barcelona kept pace with Atletico at the top of the table, after Diego Simeone's side had claimed a hard-fought 1-0 win at home to Villarreal earlier in the day.
He said: "In a sense, I was expecting today's 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.
"I don't want to make excuses. The feeling that I have is that in between the game this past Tuesday (against Atletico Madrid in the UEFA Champions League) and the one next Wednesday (in the second leg) this match against Betis snuck up on us.
"We needed to win in order to continue putting pressure on the leaders."
"I wanted to rest some of the players ahead of Wednesday's game against Atletico if today's game had gone differently. It didn't play out that way," he 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 rotations."
