The Welsh outfit slipped to 17th in the Premier League table, three points outside the bottom three, after losing to another of their relegation rivals in Bournemouth on Saturday.
Having been beaten at Hull City the week before, Swansea's next match against fellow strugglers Middlesbrough on Sunday, April 2 has taken on added importance.
Fer believes the Swans missed a golden chance to move clear of the relegation zone in their last two matches but is now eyeing a return to winning ways when Boro come to town.
"Middlesbrough is the game we need to win, that one is massive," he told BBC Sport. "We have a massive game now against Middlesbrough.
"Our injured players can come back in the international break now, Martin Olsson and Kyle Naughton. With a good group, we can focus on the next game.
"We had a good opportunity to get clear (in the last two games), but that opportunity is not gone, we play Middlesbrough next.
"The last two games have not been our best week, the things we were doing before, we have to start doing again."