Watford manager Quique Flores has told Jose Holebas that he must improve if he is to win back his place in the starting lineup.
The summer signing from Roma started the season as Flores's number-one left-back, but he has not featured since late August and did not make the bench for either of the club's last two Premier League matches.
When asked by reporters why that was the case, Flores responded: "I chose Holebas in the first matches to play in this position. But the performance of Holebas is not enough to keep him in the first XI.
"It's very easy for me if I think that is not enough, I need the player to train better. Holebas understands because he is an experienced player.
"Maybe when he arrived, he thought it would be easy to play at Watford, but the level of the team is high. There is competition for positions."
Flores also refused to confirm if the 31-year-old would be included in the squad for the weekend's trip to Bournemouth.