Middlesbrough boss Aitor Karanka has conceded that he was frustrated with his side's inability to beat Birmingham City in their Championship clash.

The North-East outfit were unable to break through the resilient Blues backline in difficult conditions at the Riverside Stadium.

Birmingham keeper Tomasz Kuszczak made several fine stops in the contest to deny Boro's forwards, and David Nugent's lack of success in front of goal boiled over when he was dismissed in stoppage time for violent conduct.

Karanka told BBC Sport: "I'm disappointed because it's difficult playing at home always trying to win games, against sides that are wasting time.

"So you can understand his [Nugent's] frustration, but you have to learn not to do that. He knows he's made a mistake but it's up to the other players on Tuesday to make up for this.

"We should have scored four goals in the first half. We created chances but didn't take them. The conditions with the wind and the rain didn't help but we still created a lot of chances. Birmingham created chances too, but I sent the team out with the message not to make any mistakes because the conditions weren't easy."

Boro are second in the standings, two points behind leaders Brighton & Hove Albion.