Schalke confirmed Tottenham have contacted the German club over a January move for Lewis Holtby.
Spurs have already agreed a contract with the German international to move to White Hart Lane in the summer, with his current deal with Schalke expiring at the end of the season.
However, with Sandro ruled out through injury for the rest of the season, Spurs have looked at the possibility of bringing in Holtby in the January window.
"Following consultation with the knee surgeon, the club can report that Sandro is expected to be sidelined for the rest of the season after surgery on his right knee earlier this week," Spurs said in a statement on their official website.
"The Brazil international was forced off during Saturday's game against Queens Park Rangers after injuring both his anterior cruciate ligament and lateral meniscus."
Andre Villas-Boas is desperate to add some bodies into his squad due to the injury, with Holtby now likely to join Spurs by the end of the month. Spurs are also reportedly tracking Yann M'Vila, who is close to agreeing a move to QPR and Mohamed Diame.
"We are in talks about a move in this transfer period, but there is no agreement," Heldt told Sky Sport.
"Tottenham contacted us, because they want Lewis now. We will decide in the coming days."
Meanwhile, Swansea manager Michael Laudrup has revealed the club have received several bids for forward Danny Graham, who is keen on a move away from the Liberty Stadium after seeing his chances diminished following the arrival of Michu this season.
"Everywhere it is saying there have been some official bids, it is true, but apart from that I don't really have any comment as in the next four days we have two very important games," Laudrup told reporters.
"Saturday is a very important home game against Stoke in the league as after that we have two difficult away games against Sunderland and West Ham, and we all know about the game on Wednesday (the semi-final second leg of the Capital One Cup against Chelsea), so that is much more important.
"So my only comment is we have had some bids and I don't want to go into detail about what clubs they are."
Laudrup also refused to be drawn out on his interest in striker Kenwyne Jones, whose Stoke side take on Swansea on Saturday. "He (Jones) will probably play," Laudrup said. "Maybe if he can play with us it can be 12 against 10 but I don't think that will happen.
"Let's just say it is not the proper time to talk about a player when he is playing against us in around 24 hours time.
"Let's hope tomorrow (Saturday) he does not have too good a day as it is better for us."