Prodi was red-carded late in the narrow defeat to Chelsea in midweek so he will miss the final game of the campaign.
Fellow defender Christian Kabasele is doubtful with a hamstring injury and Miguel Britos is suffering from a calf complaint and is not likely to be risked.
Watford will be keen to enter the summer with a positive result as they have lost five consecutive Premier League games.
It is their worst run since the 2008-2009 season and they scored just four goals in the last seven matches, all of which will have gone some way to the axing of head coach Walter Mazzarri earlier this week.
Sheffield United could have leading scorer Leon Clarke back for their home game against Nottingham Forest.
St Johnstone midfielder Murray Davidson is determined to use their derby exploits as a springboard to rid them of inconsistency.