The Uruguayan’s close-range finish capped a dominant performance by Boro, who were still forced to cling on for a point after Adama Diomande missed two golden chances in injury time.
The home side’s first win in four games steered them clear of the relegation zone and Karanka said: “It’s massive because they are a direct opponent and apart from the score we showed we are better than them.
“For 70 or 75 minutes we had the possession and the chances and we controlled the game. We don’t have the experience that other teams have and for us every single point is really important.
“I can imagine how the players felt on the pitch so I think it is a really good win because adding more points onto the table will add the experience.”
Karanka refused to single out Ramirez for special praise despite his match-winning display before he had to be substituted late on with what the Boro boss dismissed as a suspected case of cramps.
He added: “I don’t want to say anything about one player because I don’t need to say how good Gaston is and how important he is for the team. Today has been a team victory because all the players have come with a really good attitude.”
Hull boss Mike Phelan admitted he had no explanation for his side’s flat performance coming so soon after their dramatic penalty shoot-out win over Newcastle in the EFL Cup quarter-finals last week.
But he maintained another defeat made no difference to his side’s belief that they can rally in the new year and claw their way out of the Premier League relegation zone.
Phelan said: “I don’t think it will kill the sense of belief because we know exactly what the purpose of this season is - we knew it was going to be difficult and we knew that wouldn’t change by winning here today.
“But it certainly makes it more difficult looking at the programme we’ve got coming up, and the rest of December and January are going to be very hard.”
Having worked briefly with Ramirez at Hull, Phelan expressed disappointment with the way his side failed to deal with Viktor Fischer’s corner which served up a rare headed goal for the Boro midfielder.
“Gaston is a talented individual who has settled really well at Middlesbrough but what really disappoints me is that Gaston has scored with a header because having known him that’s not one of his fortes.
“It’s disappointing because we had our set-piece jobs to do and we needed concentration and we lacked it at that moment in time.
“When it came to game certainly the possession wasn’t in our favour but we had a few flash chances and but for a few incorrect decision-making moments we could have done better and possibly could have got a goal.”