Chelsea youngster Patrick Bamford could yet be loaned back to Middlesbrough for the 2015-16 season if the club win promotion to the Premier League via the play-offs.
The 21-year-old has scored 17 goals this season to help Boro to a fourth-place finish in the Championship, setting-up a semi-final meeting with Brentford for a place in the play-off final against Ipswich Town or Norwich City on 25 May.
Bamford was expected to return to Chelsea where he would either be sent out on another loan spell or be involved in regular first-team duties, with manager Jose Mourinho keen to promote players who have emerged from the club's youth ranks.
Formerly of Nottingham Forest, Bamford has spent spells on loan at Milton Keynes Dons and Derby County over the past two seasons but has stated his intent to return to Stamford Bridge.
However, ahead of the first leg of the play-off semi-final against Brentford, Karanka has revealed an agreement has been reached with Chelsea over the forward's future that could see him return next term.
"I would like to keep him because he is the top scorer this season and, for everybody, it was a very good decision for him to come here," he said.
"He has improved a lot, and the other players are very happy with him. Chelsea are happy because he is a better player now, and of course I would like to keep him with us, but the most important thing for that is that we are in the Premier League [next season].
"Patrick has shown this season that he is a Premier League player and, for that reason, if we are not in the Premier League, I think he will have other chances to play in that division. But we have to think first about the game Brentford tonight and then the game on the following Friday, that is the focus."