Messi went down in agony and is now expected to be out for three weeks with an ankle injury, as the Czech center-half received his marching orders late in the Liga clash.
"I'm sorry. I would like to publicly apologize, because, honestly, it wasn't my intention," Ujfalusi told a news conference.
"I tried to go for the ball, but naturally, with the speed he had, he also could not stop and I was unlucky as my foot stepped on his ankle."
Brutal
Meanwhile, Messi's teammate David Villa slammed Ujfalusi for the challenge, which he believed was 'brutal'.
"We all saw the tackle on television and it seemed like a horrifying, brutal challenge," said the Spain striker.
"I don’t think that Ujfalusi did it with the intention of hurting Leo but for sure the next time he’ll think twice about it.
"If he said it was bad luck we have to believe that rather than judge him."
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