A 58th minute strike from Spanish midfielder David Lopez saw the Seagulls climb to sixth, but Crofts had to be helped off shortly before the finish and Garcia is worried the injury could be a serious one.
He said: "I'm not 100 per cent sure, but the injury could be a bad one. We won't know until he has a scan and we see the result.
"It's the worst news of the day and sad for Crofty because he's been having a terrific season."
Garcia played down Albion's elevation to the top six by insisting he was no happier than when his men had won previous games.
He said: "I prefer to see the performance of the team. Some games we played well yet didn't win. We have to keep going and at the end of the season we'll see where we are."
Brighton clinched victory without midfielder Liam Bridcutt, reportedly a target for former boss Gus Poyet at Sunderland, but Garcia stressed he missed the game due to a groin injury.
The Spaniard added: "He's not 100 per cent and we need people 100 per cent to play. If he is fit enough I will play him. We want to keep him because he is one of our main players."