Crystal Palace could be without the injured Scott Dann, who missed the midweek defeat at Manchester United along with several other first-team regulars.
James McArthur made his comeback from an ankle injury at Old Trafford but he is unlikely to start on Sunday.
Watford also rested players in midweek and Troy Deeney and Odion Ighalo are among those expected to return.
Nordin Amrabat is suspended following his sending off at West Ham.
MOTD COMMENTATOR’S NOTES
Simon Brotherton: “This is a match that brings back memories of a tense Championship play-off final between the sides three years ago, which was decided in Palace’s favour thanks to a Kevin Phillips penalty in extra-time.
“This game could be just as tight and looks equally hard to call, not least because both sides have struggled for form since the turn of the year. Palace have won just one of the last 15 in the league, Watford only two more.
“Both Premier League meetings this season resulted in away victories, so at least each set of supporters will turn up feeling they’ve got a great chance of getting to the final.”
There seems to be a bit of speculation over Watford manager Quique Sanchez Flores’ future. That seems harsh after the season they have had.
- Think you can do better than Lawro? Predict the score for this match and the rest of this round’s Premier League fixtures in our Predictor game.
- Crystal Palace beat Watford 1-0 after extra time in the Championship play-off final at Wembley during the 2012-13 season.
- Watford have lost only one of six previous FA Cup ties with Palace (W3, D2), a 1-0 fifth-round defeat after extra time in 1995.
- Palace have won seven of their last 11 meetings with the Hornets in all competitions (D2, L2).
- Crystal Palace have reached their first FA Cup semi-final since 1995, when they lost 2-0 to Manchester United in a replay.
- Their only semi-final win in four attempts came in 1990 when they beat Liverpool 4-3. Current Eagles manager Alan Pardew scored the winning goal that day.
- The Eagles have beaten Premier League opposition in three of their four FA Cup ties this season, knocking out Southampton, Stoke and Tottenham.
- Palace could keep four successive clean sheets in the FA Cup for the first time since 1924.
- Crystal Palace goalkeeper Wayne Hennessey has conceded only one goal in four FA Cup ties.
- Watford have reached the FA Cup semi-final for the first time since 2007. They have lost four of their five previous games at this stage, but did beat Plymouth Argyle in 1984 to reach the final.
- They have beaten two Premier League sides en route to the semi-finals: Newcastle and Arsenal.
- However, they have only won one of eight Premier League matches since beating Crystal Palace in mid-February.