The Greece striker was forced off the park 10 minutes from the end of last weekend's 2-1 win at Partick Thistle after suffering a deep gash to his knee.
The injury required stitches and manager Neil Lennon is unlikely to risk his Champions League talisman just four days before the 'return' against Ajax at the Amsterdam ArenA.
However, there was better news for Lennon when full-back Emilio Izaguirre, who like Samaras missed the final stages of the Thistle game with a head injury, was passed fit to face Jackie McNamara's side.
Midfielder Joe Ledley was rested on Friday due to a back problem but should be ready to play while James Forrest (ankle) and Charlie Mulgrew (heel) are back in contention for a start.
But Lennon is unlikely to rush back Kris Commons with the Ajax tie in mind after the midfielder sat out the trip to Firhill due to a hamstring strain.
Nadir Ciftci is available for Dundee United as he awaits the appeal against his red card at Inverness and hearings over misconduct charges.
But the visitors have a slight doubt over keeper Radoslaw Cierzniak who is carrying an ankle injury from the extra-time League Cup defeat against Caley.
Andrew Robertson has been suffering from a dead leg but McNamara is confident the United defender will be available.