Fernando Torres's relief at escaping an additional three-match suspension for scratching the Tottenham Hotspur defender Jan Vertonghen has proved short-lived after the striker damaged knee ligaments 36 seconds into Chelsea's victory at Steaua Bucharest.

Torres appeared to open up the joint in his left leg as he challenged Steaua's Cristian Tanase in his side's impressive 4-0 Group E success in Romania, the forward eventually limping from the fray after 11 minutes.

The 27-year-old, who is banned from Sunday's trip to Norwich after receiving two yellow cards at White Hart Lane, will undergo a scan at Cobham on Wednesday and, although Chelsea are confident he has not sustained an injury to his cruciate, there are fears over his medial ligaments.

If that is confirmed he may be confronting an absence of up to six weeks. "The doctor is very confident it is not a big injury like we had with Marco van Ginkel," said José Mourinho, referring to the Dutch midfielder who underwent surgery last week after rupturing a cruciate ligament at Swindon and has been ruled out until March. "But it's something with his knee, his ligaments, and we have to wait for the scans. He knew he wouldn't play against Norwich and now he knows he cannot go away with the national team.

"If the injury can be recovered in 15 days then he will be fine for our next match, against Cardiff. The problem is if it's more time. It's a pity for the guy because, physically, he was in a very good moment. He played fantastically against Tottenham and deserved to start this game. That's the bad news."

The good related to confirmation that Torres will not face a violent conduct charge for his claw at Vertonghen's face, a decision Mourinho welcomed but which has exposed the limitations of the Football Association's new powers to take retrospective action.

Chelsea expected to have the striker banned for a further three matches after television footage captured him scratching the Belgian centre-half's cheek five minutes into the second half on Saturday.

The referee, Mike Dean, booked Torres for tripping Vertonghen in the buildup to their altercation but the fact he had not then witnessed Torres raising a hand to his marker had potentially opened the possibility of the FA referring the incident to its new three-man panel of ex former referees. However, having taken statements from all the officials at White Hart Lane, the governing body determined that the assistant referee closest to the incident, Jake Collin, had seen "the coming together of the two players, albeit not in its entirety".

Torres's scratch had been to the left side of Vertonghen's face, with the assistant on the other side of the players and therefore unsighted. But, because the linesman had effectively seen the forward raise his a hand, the FA concluded it could not refer the matter to its panel.

Incidents that have been seen by officials, even in part, can be referred only in"exceptional circumstances" and the FA did not consider this matched that criteria. Incidents such as Luis Suárez's bite on Branislav Ivanovic and Eden Hazard's clash with a ball-boy would be considered exceptional and worthy of more than the standard three-match suspension.

Torres's subsequent dismissal came when Vertonghen appeared to suggest serious contact after an aerial challenge between the two, an overreaction that continues to rile Mourinho.

"There was quite a real pressure to make him have two or three matches ban," said the manager. "But, at the same time, I was more than confident because I think the FA defends the interest and culture of English football, and defending English football is not to protect people who cheat and simulate. To protect English football and the culture of English football is to protect people who play the game with emotion, and make everything English football what it is. They punish when you don't respect the integrity of game by simulating."

Mourinho was in better spirits after seeing his side dismantle Steaua to re-establish their credentials in Group E. "We've put ourselves in a more balanced position," he addedsaid. "If we hadn't won today we'd have been in trouble, but we cleansed a little bit the fact we lost the first game [against Basel].

"Now everything is there. We have a double fixture against [the group leaders] Schalke, so it's open. We played a very good game from minute one."