Watford striker Stefano Okaka could be sidelined for several weeks and will miss this weekend's home game against Manchester United.

The summer signing suffered a muscle injury at West Ham United and will not feature at Vicarage Road on Sunday.

Walter Mazzarri's side could also be without defenders Younes Kaboul and Sebastian Prodl with their fitness in doubt ahead of the Premier League clash.

Nordin Amrabat was deemed not fully fit last weekend but the Moroccan international is fit to feature this weekend.

Head coach Mazzarri said: "I need to verify today and tomorrow Kaboul’s condition and also Prodl had a problem during the week.

"Okaka also won’t be available. At the moment this is the situation so I need to verify it at the last minute."