Bluebirds chairman Peter Ridsdale has confirmed that United and Arsenal have been looking at the highly rated 17-year-old.
Wales full-back Matthews told BBC Sport Wales: "If that ever came about I'd have to think about it.
"But I'm just happy to be playing for Cardiff at the moment."
A move to a major Premier League club would mean Matthews following in the footsteps of another recent Bluebirds academy player, Aaron Ramsey.
"I don't think the speculation is distracting," he said. "I'm quite a level-headed boy and obviously I'm very happy to get noticed.
"But I'm happy to be with Cardiff and play the rest of the season and I've heard nothing. It's just rumours.
"My ambitions are just to play as much as I can and play well and hopefully the team can get promotion to the Premier League.
"I think we've got as good a chance as any. We've got a good squad here and if we keep the key players fit, I think we can make a good push for it and I think we can do it.
"Every player wants to play against the best players in the country so if that ever happens, I think that's a good motivation for us to get promotion."