Injury-hit Watford look set to be without Roberto Pereyra ahead of the trip to Sunderland tomorrow.
Pereyra suffered a knee injury against Manchester City on Wednesday night, and attempted to play on before admitting defeat.
He is unlikely to be fit for the game at the Stadium of Light, with Hornets boss Walter Mazzarri admitting it is a concern.
Mazzarri said: “I asked him if he felt a twist in the knee.
“They (medical staff) told me it was a knock and that’s the reason he went back on the pitch. Now, I’m not sure.
“We have not been lucky with injuries recently and it’s not an easy moment for us.
“We’re not happy with the injury for Pereyra and hopefully he is back soon. We will verify in the next few days.”
Watford have the joint third highest number of injured players in the Premier League, with seven stars now in the treatment room.
However two of them – Valon Behrami and defender Craig Cathcart – could return for the Sunderland clash.
Behrami has been ill while Cathcart is recovering from a hernia problem.
Still missing are Stefano Okaka (hamstring), on-loan Chelsea star Kenedy (knee), Brice Dja Djedje (foot) and defender Adrian Mariappa (knee).
Sunderland may be bottom of the Premier League, but they top the table in terms of injuries with nine first-team players out of action.
David Moyes will wait to see if Victor Anichebe, Javier Manquillo and Steven Pienaar, who all missed the game against Chelsea in midweek, are fit to return this weekend, while he must check on Billy Jones who was forced off on Wednesday night.
Duncan Watmore and Paddy McNair are out for the rest of the season, while Lee Cattermole and Lynden Gooch are long-term absentees. Jack Rodwell is a couple of weeks away from returning also.