Borussia Dortmund chief executive Hans-Joachim Watzke remains hopeful Marco Reus will return to first-team action this month.
An adductor injury sustained at the tail end of last season ruled Reus out of a place in the Germany squad for Euro 2016, and he is yet to feature in 2016-17.
Last month Dortmund coach Thomas Tuchel revealed the attacking midfielder's planned re-integration into full training had been delayed by "a few days".
Reus was expected to return to first-team action in mid-September and Watzke hopes that target will not be too far off.
"I do not know [when he will be back]. Let's see, I'm not a doctor," he told reporters ahead of Dortmund's Champions League meeting with Legia Warsaw on Wednesday.
"We have had a few delays so far. Today is the 13th and September has 30 days, so we still have 17 days [to get him back this month]."
Dortmund head into their Champions League opener against Legia on the back off a 1-0 Bundesliga loss to RB Leipzig, and Watzke is keen to see immediate improvement.
"There are only six group games, so you can't allow yourselves many slip-ups. On the other hand it will be a similar situation to the one in Leipzig," he said.
"They will go into the match with the same euphoria and the same passionate support that Leipzig had in our Bundesliga match at the weekend.
"We need to be prepared for this. It would be great if we could pick up some points in Warsaw."
Dortmund mustered just one shot on target in Saturday's loss, and the lacklustre performance in the final third did not go unnoticed by Watzke.
"Obviously there is a whole host of things to improve. Leipzig were also very strong opponents, but we can play the better football," he said.
"There would have been two or three gilt-edged chances if the final ball had reached its destination. That's something we need to improve."
Julian Weigl is set to make his Champions League debut in Warsaw despite a heavy blow to the nose against RB Leipzig, and he is pleased he will not need to sport any protective gear.
"I am of course looking forward to my first Champions League game. When the anthem is played it will be a special feeling," said Weigl.
"The headaches are gone now. I do not need a mask, which is the most important thing. I think that would have hindered me."