Doohan is a product of Celtic's youth set-up and had loan spells with Cumbernauld Colts, Greenock Morton, Ayr United, Ross County, Dundee United and Tranmere Rovers before joining the League Two club permanently in 2022.
After a only half a season there, the Scotland Under-21 cap moved up to League One with Forest Green Rovers, but following their relegation, he joined Aberdeen the following summer.
Doohan has been the back up at Pittodrie, playing only twice in his first season and 18 times in the latest campaign while Bulgaria's Mitov was injured.
With his contract expiring, he has left Pittodrie and is being linked with a return to Celtic, where the 27-year-old would likely be back-up to Kasper Schmeichel and Viljami Sinisalo.
Doohan offers Scotland more experience, having played over 180 first-team games in comparison to Slicker's tally of just seven, but what else does he bring?
An injury-time penalty save from Hearts' Jorge Grant was his personal highlight of his season at Aberdeen, ensuring his side earned a goalless draw in January.
That game was one of fifteen Doohan played in the Premiership last season.
Across those matches he conceded 27 league goals, an average of 1.86 per game. And his save percentage of 56% was the joint second worst in the division.