Shearer, who is now a pundit for Premier League Productions, spoke about whether the English forward is good enough to lead the line for the Gunners.
Nketiah was sub par in a tough 1-0 win for the Gunners against Everton on Sunday in the league.
“We will keep on asking those questions because it's important that when he gets the opportunity like he has done, then he has to take those opportunities.
“I just thought there were two or three occasions against Everton, one being the disallowed goal. There were a couple in that second half where I was thinking 'come on. Get on the end of it and into the six-yard box and that little tap-in, like all great strikers do'. It was just a split second where he was slow.
“Until he does that, then those questions are still going to be asked."