Manchester City boss Mark Hughes has admitted that Robinho is unlikely to face Schalke.
The Brazilian was substituted in the second half of City's 3-0 victory over Arsenal on Saturday after picking up a knock.
His ankle is still swollen and Hughes does not want to gamble on his fitness in Thursday's Uefa Cup game against Schalke, especially with the Manchester derby coming up at the weekend
"The medical staff will have another look at Robinho before we leave but if his ankle is as sore as it was yesterday then he definitely will not travel," Hughes told the Manchester Evening News.
Robinho has made an excellent start to his Premier League career and is looking to continue his fine form against United.
He is also confident that City can challenge for Uefa Cup glory after recording a 3-2 victory over FC Twente in their opening Group A match.
"We can win the Uefa Cup, it is one of our targets," he said.
"We know we are a side that is developing and growing but we also know we are capable of great things when we play well. We have shown that in many games.
"The rest of the players and me admire the ambitions of the owners of this club. We all want to strive to make City one of the best in the world. I want to stay here for many years and make history. Doing well in the Uefa Cup would be a great way to start.
"As for the derby, I enjoy playing in the big matches, of course I do. The Madrid against Barcelona games were great to play in but classics are classics in any country.
"The Manchester derby is a huge game and I hope we win because I know how important it is to our supporters.
Robinho added: "United have some great players including (Cristiano) Ronaldo who I am yet to meet but they are not just a one-man team.
"They have (Wayne) Rooney, (Carlos) Tevez and other very good players. I hope we perform to our optimum level and if we do then we will expect to take all three points."
Gelson Fernandes, meanwhile, has been ruled out for up to three weeks with a pulled hamstring.
The Swiss midfielder suffered the problem on international duty last week and could now miss four matches for City.