Vallejo stepped in when Hogg missed Tuesday's 3-2 win over Blackburn Rovers with an abdominal injury. The Spaniard opened the scoring but had to make way for High in the second half.
He and Levi Colwill, who missed the match with an ankle problem, will be assessed ahead of the trip to Kenilworth Road.
"He was having a pain in the knee and has been assessed," said coach Carlos Corberan when asked about Vallejo in his Friday morning press conference. "He's now with the doctors so I won't know how he's going to be until after that.
"We'll see if he trains and if he does, he's going to be one of the options for us. If he's not training he's not going to be with the group.
"All the (other) players that were available on Tuesday are, it's only Alex who is a doubt.
"Hoggy and Colwill are being assessed and before training I will know if they can take part. If they react well to training I will know if they are ready for tomorrow or if they are out of the group."
Naby Sarr deputised for Chelsea loanee Colwill on Tuesday, and can be expected to again if the teenager is unavailable.
Jordan Rhodes is back in training after a back injury, but is still some weeks away from returning to first-team football.