SHAUN Williams is "at least a week" ahead of schedule as he recovers from a knee injury – with the midfielder set to be available for the packed Christmas programme.
Williams, 31, is back in training this week though he won't be taking part in any contact work for two weeks.
The midfielder was expected to be out for three months after suffering lateral ligament damage in his knee against Reading on September 26.
Millwall face three games in six days from December 23 when they travel to Derby followed by Wolves on Boxing Day and then QPR, both at home.
Harris praised Williams' "professionalism" that has put him in the frame for those fixtures.
"Shaun saw the specialist on Monday and he's back outside on the pitch," Harris said. "He's in the position exactly where we hoped he would be.
"The reason he is in that good position, in good health and his knee has healed and his quads are strong, is because he has worked so hard.
"That's enabled him to be at least a week head of where he should be, because of his professionalism.
"It'll be nice for everyone to see Shaun back out on the grass.
"He's not going to be fit or available in the next couple of weeks. He has to do straight-line running, diagonal running to test and strengthen the knee. He'll go back into full training for a week and then get some minutes in an under-23s game. Once he does that he becomes available for the squad and certainly for the Christmas period."
Meanwhile, centre-back Jake Cooper is available again this weekend after serving a one-match ban for his sending-off at Sheffield Wednesday.
Harris admitted that presents a tough selection call after Tony Craig did little wrong against Burton two weeks ago.
"I have the opportunity to put Coops back in," Harris said. "He's another one that the rest has probably done him good, from being out of the team to then playing a lot of games in a short space of time.
"Tony was very assured against Burton, as you'd expect from the club captain. There is certainly a decision to be made at centre-back for Saturday."
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