Patterson won't make a Premier League GK. He has barely improved 150+ games later and consistently has a goals prevented rate that has him exactly mid-table in the Championship.
People look at age but there's a far better correlation between games played rather than age, and he's relatively experienced considering the amount of games he has played.
There's a reason the club have been linked to the likes of Bulka and Petrovic and now signed Roefs, and why newspaper style links of Patterson himself going to PL clubs never had any substance.
This talk of keeping tools sharp and polished is cliched gibberish. He's 25 now, has had 3 full seasons at Championship level playing over 130 games in that division and has been given a lot of rope during that time too. It's not going to happen for him at the highest level, and the club are obviously wise to that too given our attempts to sign a GK all summer.