Manchester - Manchester City have been dealt a blow after German midfielder Ilkay Gundogan sustained a knee injury that manager Pep Guardiola fears will sideline him for "several months".
The Germany international had to be substituted in the 44th minute of City's 2-0 Premier League win over Watford at the Etihad Stadium on Wednesday after an accidental collision with Nordin Amrabat.
Guardiola revealed afterwards he had sustained suspected knee ligament damage.
"We are going to miss him for a long time," said Guardiola. "This is the worst news.
"I'm so so sad. The doctors think he has ligament damage, but he doesn't know exactly (how serious it is).
"We will know tomorrow (Thursday), but it doesn't look good. I think it will be several months. He is so sad about it."
Gundogan, 26, joined City from Borussia Dortmund in June for a reported fee of 20 million ($25.1 million, €23.8 million).
He had dislocated his kneecap in May while training with Germany, which ruled him out of Euro 2016.
Spinal surgery had previously cost him the entire 2013-14 campaign.
Initially sidelined after undergoing surgery at the end of last season, he has impressed since making his debut in a 4-0 Champions League win over Borussia Moenchengladbach on September 14.
To date Gundogan has made 15 appearances for City in all competitions, scoring five goals.
His injury cast a long shadow over a home victory for City - their first since beating Bournemouth on September 17 - that was secured by goals from Pablo Zabaleta and David Silva.
"Football is emotional when you don't get the results you expect," said Guardiola, whose side had lost to Chelsea and Leicester City in their two previous league games.
"The last three or four games at home weren't good in terms of results, but today we won.
"We are going to analyse the result, but we have to focus on the result because today the players showed me again the form they showed at the beginning of the season.
"From here, the players are going to take more confidence. I'm pretty sure of that, especially with the players we have to come back.
"And I am happy with the clean sheet, but I am so sad for Ilkay Gundogan."
Zabaleta echoed his manager's comments about the importance of the victory after scoring his first goal in over two years.
"It has been a long time without a win playing at home. It has been strange," he said.
"We had the clean sheet we've been talking about and were solid defensively."
Zabaleta is out of contract at the end of the current season and not expected to remain with the club, but Guardiola paid tribute to the veteran Argentinian defender.
"We need his spirit. He is part of this history and played well with and without the ball," said the former Barcelona and Bayern Munich coach.
"On the pitch and in the dressing room he is important for us."
Watford manager Walter Mazzarri has injury concerns of his own after midfielder Roberto Pereyra came off after half an hour.
"The problem is his knee," said the Italian. "And we need to understand what it is exactly, because we still don't know. We will know in the next few days."
Mazzarri chose to rest striker Troy Deeney ahead of the weekend clash with Sunderland, handing a first start to 20-year-old Jerome Sinclair, a 4 million close-season signing from Liverpool.
"We have had three games in a week and also Troy has four yellow cards," said Mazzarri. "Also I wanted to get him in good condition and be ready for the game against Sunderland.
"Jerome worked a lot for the team, and the entire squad. He sacrificed a lot. He was a reason they didn't have many goal opportunities. He did very important work all around the pitch."