The former England midfielder smashed home a stunning winner to edge Premier League Boro to a 1-0 fourth round victory over League Two Accrington, capping an impressive individual display on his return to the starting line-up for the first time since New Year’s Eve.
Downing has been linked with a move away from the Riverside Stadium this month, but Karanka insisted after the game that he remains part of his plans.
Karanka said: “I don’t know who was speaking. I have said Stewart was an important player for us at the start of the season. He is one of the few players who has Premier League experience.
“Once again, I showed that I trusted him today and when I can give him a chance, I will.
“It wasn’t a coincidence because I told him at half-time that he was one of the best players on the pitch. He has not been playing and he went on to the pitch and showed he wants to play and is ready to play.
“Always when a player takes his chance, he is a player that you have to consider.”
It took Boro 69 minutes to find a way through the Accrington defence on a day when chances went begging.
But Downing was not found wanting when he took aim from 25 yards and drilled the ball past keeper Marek Rodak and into the top corner to book a place in the hat for the fifth round draw, although Stanley midfielder Sean McConville wasted a glorious opportunity to level with seven minutes remaining.
Karanka said: “I think we were good. It’s difficult sometimes to play these kind of games because everybody thinks it’s going to be an easy game. You can look at the scores in the other games and a lot of good teams have lost, teams in the Premier League and at the top of the Championship.
“We created a lot of chances we didn’t score, but the most important thing today was to win the game.”
Accrington boss John Coleman was disappointed by the defeat and admitted a replay could have been a “godsend” for his club.
Coleman said: “To only lose 1-0 - we haven’t embarrassed ourselves. I know it’s probably the last thing Middlesbrough needed, but a replay would have been a godsend for us financially.
“It probably would have been on the telly and a big gate and it would have enhanced our chances for what we do next year.
“These games probably don’t have the impact on Middlesbrough that they could have on us long-term.
“I’m disappointed that we were beaten because you’ll always be annoyed if you lose. You don’t come here to be beaten.
“Obviously we are disappointed at losing - we don’t want to be plucky losers. We came here with a game-plan for trying to win the game.”
Meanwhile, Karanka was remaining tight-lipped about the possibility of signing Paris St Germain’s Jese Rodriguez as the transfer window draws to a close.
He said: “I don’t know anything and I don’t want to know anything because we have a game on Tuesday. I don’t want to know anything about new players, or players leaving, or players coming.”
Middlesbrough: Konstantopoulos, Friend, Bernardo, Gibson, Da Silva, Fischer, Clayton, Leadbitter, Downing, Bamford,
Gestede. Subs: Negredo, de Roon, Stuani, Fry, Valdes, Forshaw, Traore.
Accrington Stanley: Rodak, Boco, Donacien, Beckles, Hughes, Rodgers, Conneely, Clare, Davies, Kee, McConville. Subs: Clark,
Gornell, McCartan, Hewitt, Chapman, Edwards.
Referee: Anthony Taylor (Cheshire)