Sergi Canos is set to miss out through suspension after picking up his fifth yellow card against Leeds.
Mads Bech Sorensen is set to return after overcoming the virus and could reclaim his place in the starting lineup.
Adam Masina will be out for a short period of time after scans revealed a minor thigh strain.
Francisco Sierralta has begun to build up fitness after suffering a hamstring injury last month.
Ken Sema returned to full training following a knee issue and is in contention for a place in the side.
Brentford: Fernandez; Pinnock, Jansson, Goode; Henry, Janelt, Norgaard, Onyeka, Sorensen; Wissa, Mbuemo
Watford: Bachmann; Rose, Cathcart, Troost-Ekong, Femenia; Kucka; Pedro, Sissoko, Cleverley, Dennis; King
Brentford defeated Watford 2-0 in May as Toney equaled the Championship goal-scoring record.
The Bees thought they had taken the lead through Marcus Forss in a first half they were on top of, but the goal was disallowed.
Just 53 seconds into the second half, Forss did grab the opener, slotting home from close range.
On the hour mark, Sierralta fouled Toney in the box and he beat Ben Foster from the spot to double the lead.
The goal was Toney's 30th, matching the record set by Glenn Murray with one match to spare.
The match will be televised on Sky Sports Premier League from 7pm. Kick-off is set for 8pm.