The Argyle boss must choose between Jake Cole and Luke McCormick when they line up against Southend on August 3.
Cole held the number one position for the majority of last season while McCormick is yet to make his first league appearance for the Pilgrims since re-joining the club back in May.
"I'm looking at both of them and it's going to be hard for me to make a decision for the first game," Sheridan told the club's official website.
"They are very evenly matched; they both work well together; and they want each other to do well. It's good to have competition - it ups each other's game.
"They know what I'm like. I don't pick any favourites - I pick who I think should be playing. We've got two good keepers. Whoever plays, I have full confidence they can do well for the team."