The England captain has yet to fire for club or country so far this season, following his attempt to leave Spurs in the summer.
Rooney thinks the criticism of Kane has been unfair and believes the 28-year-old can get close to Shearer's record of 260 goals.
The Derby boss told Sky Sports: "I personally think it [criticism of Kane] is an overreaction if I'm being honest.
"It's the first game for a while that he hasn't scored for England and for Tottenham he's still scored a few goals this season although not in the Premier League.
"He's one of the best strikers in the world and when you don't score people have their opinions, which they are entitled to of course, but Harry is a good enough player and a big enough person to come through this period.
"It's a little bit of a sticky period for him which he probably hasn't had to deal with [previously]. All strikers deal with it and Tottenham aren't in the best vein of form themselves so that's down to the team."
On catching Shearer, with Kane sitting on 166, Rooney added: "I think the minute Harry gets his first goal in the Premier League then he'll get back to scoring on a regular basis.
"I think as a striker you're expected to score goals but I think Harry has changed his game quite a bit in the last couple of years and he is coming a bit deeper.
"He's created quite a few goals over the last couple of years as well but ultimately people will look [when you're not scoring].
"He's going through a sticky patch but there's no doubt in my mind that he will get through it."
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!