Watford have confirmed that goalkeeper Ben Foster has undergone surgery on a knee injury.
The Manchester United loan star has gone under the knife but is only expected to be sidelined for two weeks.
"Ben Foster has been worked exceptionally hard with his knee over the last fortnight," Watford physio Andy Rolls told the club's website.
"He's had a niggle there for the last few weeks and we've been very aware of that - a slight irritation to the meniscus in his knee.
"Over this period, we've been in constant communication with Manchester United and we felt that by resting from the Middlesbrough game it would sort him out.
"Unfortunately, during the game at Portsmouth on Saturday, his knee semi-locked on him while he was taking a goal kick and he wasn't happy with how it felt at all.
"In liaison with Manchester United, he had a minor operation on Monday and has already begun his rehabilitation."
Rolls confirmed that midfielder Hameur Bouazza is set for a swift return.
Bouazza damaged his ankle against Portsmouth at the weekend but scans have confirmed he has no significant damage.
"He's had a scan and, although there was a lot of swelling, there's no significant damage so he should be back soon," said Rolls.
It was also confirmed that defender Clarke Carlisle is looking to return before Christmas.
The former Leeds man has been out since the summer with a thigh problem.
"It's a condition called myositis ossificans which is rare but not totally unheard of," added Rolls.
"He's now on medication to get his bit of bone to re-absorb.
"He's still in rehab but we're hoping he'll be back in full training before Christmas."