Ten Hag: Man Utd have 'no excuses' despite injury woes
Ten Hag's side are likely to be without both players at the City Ground after they were hurt during Thursday's 2-2 draw against Sevilla in the Europa League quarter-final first leg.
Martinez was stretchered off after gripping his right ankle in the second half, while fellow centre-back Varane was substituted at half-time.
Ten Hag had no update on the condition of either Martinez or Varane when he spoke to reporters on Friday.
"It's not even 24 hours, so I don't have a complete diagnosis so I can't tell in this moment," he said.
The United boss was coy when asked about reports that World Cup winner Martinez had broken a metatarsal, which would likely rule him out for the rest of the season.
"I can't say in this moment," he said. "When we have news, we will give it straight to you.
"But let's do the medical, do the assessment, fully diagnose, complete the diagnosis and then we will give the news.
"It doesn't change in this moment. I have an idea but I don't cause speculation."
Varane's replacement, Harry Maguire, scored an own goal in stoppage time as Sevilla came from two goals down to rescue a draw at Old Trafford.
But Maguire and Victor Lindelof will likely have an important role to play after Martinez and Varane joined an injury list that already includes Marcus Rashford, Alejandro Garnacho and Donny van de Beek.
With fourth-placed United hoping to secure qualification for next season's Champions League while also chasing silverware in the Europa League and FA Cup, their injury problems could not be timed any worse.
Ten Hag hopes Luke Shaw and Scott McTominay will be fit for the Forest game, but the United boss was quick to underline the importance of squad players stepping up.
"Every game is a battle, every game is a fight and you have to be ready for that fight," he said.
"We have a squad. I have said all season we have more than 11 starters, so now others are on and when their time is there you have to show and contribute to the team.
"You have to be ready. That is what we expect, that is what we demand."
Asked if it might be difficult to blend the understudies into his starting line-up, Ten Hag said: "I think then you are finding excuses.
"If you want to find excuses or set excuses, then you don't have to play for Man United and you have to look for another club.
"You have to wait for your moment and when the moment is there you have to contribute, you have to bring your performance and that is what we demand."
