The Red Devils forced a replay on Sunday afternoon after Anthony Martial’s late equaliser rescued a 1-1 draw for the hosts at Old Trafford.
France international Dimtri Payet had broken the deadlock for Slaven Bilic’s side with a brilliant free-kick which beat United goalkeeper David De Gea.
Speaking to BT Sport following Sunday’s FA Cup quarter-final stalemate, former United midfielder Scholes expressed his concern over the Red Devils’s prospects.
“Going to West Ham, you’d have to fancy West Ham in current form and the way Man Utd are playing,” Scholes said.
“They can prove me wrong. If I had to put a marker down at the moment, I’d go for West Ham.”
West Ham are in fifth place in the Premier League table and two points ahead of Van Gaal’s Red Devils side in the race to secure a spot in next season’s Champions League.
The 20-time English champions are in action on Thursday night in the second leg of their Europa League last-16 clash.
United lost 2-0 to bitter rivals Liverpool at Anfield last week.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news