"Lewis is a great driver," Horner is quoted by the Telegraph. "You would think he's not going to be happy having another barren year."
But Hamilton also had a poor season in 2009 as reigning world champion, while last season the McLaren was not quite a match for the best cars.
Horner suggested it is 26-year-old Hamilton who will therefore be doing the knocking.
"That is not to say we are looking for him to come to our team. We are very happy with the two drivers we have. That is more of a question you would need to put to Lewis," he added.
Horner insisted Red Bull could handle a Sebastian Vettel-Hamilton pairing.
"You would certainly envisage it being quite a busy partnership, but you can never rule it out. From my perspective you always want to have the best two drivers," he said.
For now, Hamilton says he is happy at McLaren, playing down reports he is disillusioned before even racing the MP4-26.
"It's a long, long year and I have no doubts that we can compete with these guys," he said.