Head coach Aitor Karanka was left frustrated after Middlesbrough conceded a disputed equaliser at the end of their 1-1 draw with Blackburn.
Boro, who had 25 shots on goal during the match, had broken the deadlock on 83 minutes through Patrick Bamford.
However, Rudy Gestede pounced in injury time, with Boro keeper Dimi Konstantopoulos grounded and injured.
"I'm happy with my players' performance but I'm frustrated with what happened at the end," Karanka told BBC Tees.
"We have been fighting for 94 minutes, we had the three points in our hand, and for one person to take that from your hand is frustrating."
Karanka was sent to the stands for his complaints to fourth official David Coote by match official Mark Clattenburg following the incident, and was cautious with his words after the match.
"If I say everything I think I will have a problem, it's amazing. My goalkeeper is on the treatment table and there was no foul," said Karanka.
"He's bad. I don't know if he will play on Saturday (against Millwall in the Championship)."
Ryan Fredericks and Daniel Ayala were also injury concerns for Karanka during the match, with both withdrawn during the second half.
"Daniel was a bit dizzy and Ryan I think has a little bit more of a problem but we do have other players to play" added Karanka.