McClaren guided Boro through their best ever spell with a Carling Cup triumph in 2004 and a run to the UEFA Cup final two years later.
He was given a warm reception by the home fans but went home empty-handed as his side fell short of their recent high standards.
"The reception was nice but that was a long time ago and I'm more concerned with today and that wasn't us today," he said. "We were below-par and that's been very rare.
"We played at a low tempo and although I thought we bossed that game in terms of possession we lacked the urgency, penetration and ruthlessness we usually show and we got punished for it. And you could see it coming.
"But we are still in a good place and we have to get back to what we have been doing quickly and get results. We need to move on as quickly as possible and get a reaction on Tuesday (at Blackpool)."
Aitor Karanka was happy to see his Middlesbrough side clock up a second successive win.
"I'm delighted," he said. "We played very well against a good side who are trying to get into the play-offs.
"It shows everybody that when we play like a team we can beat any team in this league. I have said this before.
"We played well to beat Brighton last week and now to beat Derby too. We worked very hard and we took one chance.
"The last four or five games at home we have played well but now we scoring goals and that means you can get positive results.
"We played well against Leeds and Blackburn and created many, many chances but we drew those games 0-0. Today we created only two or three chances but we scored and we won."