Abraham has battled the issue since hobbling out of Chelsea's 2-0 win over Newcastle at Stamford Bridge on February 15.
The 23-year-old has made five appearances since that initial problem, but failed to complete Chelsea training on Thursday and will now miss Saturday's Premier League trip to Leeds.
“Tammy still has ankle pain from the tackle against Newcastle, from the same injury," said Tuchel.
“He's still not 100 per cent comfortable. Yesterday he went off, the day before he was fine, yesterday he had some training.
“Honestly I'm a bit concerned because it's still the pain from the tackle against Newcastle, so we're talking about a long time now where he does not really feel 100 per cent free and comfortable; I can see it in training.
“Even if he finishes training I see that it's not 100 per cent, that he has trust or feels totally free.
“So yeah I'm a bit concerned but at the same time I have 100 per cent trust in our medical department, those guys are fantastic and they take care of him now.
“It was a bit of a setback yesterday that he had to leave the pitch during the warm-up, but he gets all the time he needs.
“First of all it's most important he feels safe, free and zero pain, and then we can think about his comeback."
Brazil defender Thiago Silva has suffered a minor recurrence of his prior thigh problem, so will also miss Saturday's Elland Road clash.
Tuchel added: “Thiago also had a little setback in training, at the end of the training session, the day before yesterday. He felt at the very end, something around the same area where he was injured.
“So we had to take him off and he's back into a transition phase but not back in team training. So he will be out."