Coppell made eight changes for the 2-0 FA Cup defeat at Cardiff last weekend but will bring his big guns back in for the Championship clash.
That should see the likes of Liam Rosenior, Ivar Ingimarsson, Stephen Hunt and Kevin Doyle return while Shane Long will be hoping to keep his place alongside Doyle and restrict Noel Hunt to a place on the bench.
Adam Federici will continue in goal as first-choice Marcus Hahnemann will be out for another two weeks with his calf injury while Coppell will monitor the fitness of central defender Andre Bikey.
Bikey has a slight ankle problem and is to have a scan so Ingimarsson will be partnered by Michael Duberry.
Club captain Graeme Murty made his first appearance of the season at Cardiff after a calf injury but has joined Charlton on a one-month loan deal.
Watford manager Brendan Rodgers will hand a late fitness test to midfielder Lee Williamson ahead of the clash.
Williamson missed the 1-0 FA Cup win over Scunthorpe last weekend with a knock sustained in training but he should be available at the Madejski Stadium.
Striker Grzegorz Rasiak will also be hoping to force his way back into the starting XI after he came off the bench to score the winner last weekend.
Midfielder John-Joe O'Toole was booked for the fifth time this season against Scunthorpe but can play against the Royals before his one-match suspension begins.
Loan duo Jack Cork and Gavin Hoyte are expected to again start after making their debuts in the Cup win as the Hornets seek a much-needed away win.