Agbonlahor picked up a hamstring injury during last weekend's 1-0 Premier League victory at Tottenham, with manager Tim Sherwood claiming the frontman would struggle to recover in time.
While defender Ciaran Clark (knee) will miss out, Agbonlahor's situation is described as "touch and go" and Sherwood hopes to partner him with Christian Benteke at Wembley.
"Ciaran Clark suffered a medial ligament injury last week so is out," said Sherwood. "We're going to wait until the last possible minute to assess Gabby Agbonlahor.
"Agbonlahor and Benteke work together. Gabby has great pace and we're looking to utilise that if he's fit.
"The Liverpool backline will certainly take a couple of steps back if he's on the pitch."
Meanwhile, Sherwood also confirmed Shay Given would retain his position as Villa's FA Cup goalkeeper.
"He's done nothing wrong," added Sherwood. "He's a big reason why we're in this semi-final with the saves he made against Leicester."
