"We've got two more games this season and there's no guarantee he will play in either," said Bates, who has yet to see Wilkinson complete a full week's training since the England international dislocated his knee against Gloucester on September 30.
"Time is running out for him to get back on the field. If I was the Lions coach I'd be concerned about that lack of rugby."
With Ian McGeechan due to name his 2009 squad a week today, Bates has suggested that a third successive Lions tour may be beyond his star No10.
Even if Wilkinson does make an appearance against Bath this Sunday or Harlequins the following Saturday, Bates believes it would be a huge ask to then throw the World Cup winner in at the deep end in South Africa.
"We're still working hard to try and rehabilitate that knee and make sure that things are progressing," added Bates.
"The difficulty is this Lions trip is going to be really hard and physical. If you are not absolutely on your game you are going to get exposed in South Africa.
"He's a class player and you've got to take that into consideration but the poor guy hasn't played since September.
"It would be tough then to ask him to go and play against the South Africans in full flow."