Middlesbrough defender Ben Gibson ruled out for a month

Middlesbrough will be without defender Ben Gibson for up to a month, manager Aitor Karanka has confirmed.

The 21-year-old lasted just a couple of minutes in Boro's Championship season-opener against Birmingham City on Saturday before a hamstring strain saw him removed.

Chelsea loanee and Nigeria international Kenneth Omeruo replaced him, and Karanka isn't "too concerned" about Gibson's loss.

"[Gibson] will be out for between two and four weeks, it is his hamstring. However, I am not too concerned as I have other players to play," the Evening Gazette quotes Karanka as saying.

"Omeruo now looks a better player and an experienced player. For him to play at the World Cup gave him a lot of confidence and I didn't have any doubts about bringing him in on loan, as I know him very well."

Boro won the match 2-0 to get their campaign off to a winning start.