The former Hull City defender admits that the league is the Royals' main priority this season, but is hoping that his side can cause an upset and go on a good cup run.
"As a player, you want to be playing against big clubs like Arsenal week in, week out in the Premier League... so the league has got to be a priority. But that makes Tuesday night's match a bonus game," he said via Reading's official website.
"And it's not impossible. If you can get a good cup run and win a few games, suddenly you're in a semi-final and then a final - and if you win a cup, the club talks about it for years and years to come.
"We can play good stuff as we've seen this season, so let's go and test ourselves against the best.
"Arsenal are a very good side, obviously - they had won seven on the bounce before the weekend. But it will be a good test for everyone.
"The shackles are off. We'll go and enjoy the game, and everything is possible".
McShane is no stranger to facing Arsenal in the cup and was part of the Hull City side that narrowly lost to the Gunners in the 2014 FA Cup final, losing 3-2 after extra-time on the day.