Midfielder Cowie has missed the last two games with a hamstring injury but he has resumed training this week and should be available.
Striker Ellington, who is still being linked with a move away from Vicarage Road, is struggling with a knee problem and continuing to receive treatment.
Winger Jobi McAnuff had to come off with a knock during Tuesday night's 4-2 win at Nottingham Forest but he is expected to be fit.
Popular forward Tommy Smith is the subject of another bid from Reading but will play if no deal is struck in time.
Blackpool manager Ian Holloway has a host of injury concerns ahead of the trip.
Holloway is desperately short of bodies and was able to name only six substitutes on the bench during Tuesday's goalless draw at home to Derby.
Striker Daniel Nardiello (hip) and defender Danny Coid (hairline fracture of the tibia) are sidelined for at least two months.
Left-back Stephen Crainey (groin), midfielder Joe Martin (shoulder) and striker Ben Burgess (groin) all missed out in midweek and could remain sidelined.
Holloway may be about to land Paris St Germain striker Yannick Boli on a one-year loan deal after the 21-year-old joined the club on trial.
Sporting Life