Aitor Karanka admits key defender George Friend is touch and go for the visit of Brighton and Hove Albion.
Middlesbrough's hopes of automatic promotion rest on the season finale at the Riverside on Saturday lunchtime, with Boro second and Brighton third in the Championship table.
League leaders Burnley have already won promotion but Boro could yet still win the league title heading into the final round of matches.
Their main injury concern is Friend, who has been absent since being taken off with injury against Burnley two weeks ago.
The club's head coach confirmed the defender has returned to light training this week but he remains a doubt for the game.
Karanka said: "George is not training at 100 per cent with the team so I don’t know at the moment.
"But I have to positive."
If he doesn't make it then the recently crowned Premier League champion Ritchie De Laet - who has filled the left-back role in recent weeks - will again deputise.
And Karanka says he has full confidence in the title winner should Friend not be available.
He added: "George is an important player for us but if he can’t play then Ritchie De Laet is an experienced player who has played recently for us.
"He has played in and won the Premier League.
"Of course I would like to play with George but if he’s not ready I have other players."