There were fears the defender would struggle to play again this season, but Ten Hag has said he could make a quicker-than-expected return.
"Rapha is closer than Scott McTominay in this moment, but still for the coming two games they are not available," Ten Hag told a news conference on Wednesday.
"We have one training session but I think it's too soon [for Alejandro Garnacho] to be available."
Garnacho has returned to training after injury and has been handed a new long-term contract as reward for an impressive breakthrough season.
The 18-year-old has made 29 appearances in all competitions, scoring four goals, but Ten Hag has warned that his deal means the level of expectation will now increase.
"Now, it's a new start, a restart because now expectations will be higher, the demands will definitely be higher," Ten Hag said.
"He is on his way. He is a strong character and that's why he's there in the moment on this level and he did it by himself. Now more work is coming because the demands are higher, we expect more from him but it's great he made it."
After the 1-0 win over Aston Villa on Sunday, United have another chance to cement their place in the top four when they travel to Brighton on Thursday.
The two teams met at Wembley in the FA Cup semifinal a week ago with United winning after a penalty shootout, and Ten Hag is expecting Roberto De Zerbi's side to have extra motivation at the Amex Stadium.
"It's a normal reaction," Ten Hag added.
"I think everyone involved in top sport, if you get beaten you want to have revenge and that is normal. They have a huge motivation to beat us but we have to match that and do more and show more hunger than them to win this game."