Jaaskelainen, now in his 14th season at the club, will be the last line of defence on Sunday against Stoke at Wembley in the FA Cup semi-final.
Eyes on the prize: Jaaskelainen will be desperate to book an FA Cup final spot
Steinsson, who played for Young Boys in Switzerland and AZ in Holland before arriving at Bolton in 2008, said: 'Jussi is a fantastic goalkeeper and I really enjoy working with him.
'He is probably the best professional I have ever worked with. We have really good professionals at the club, who work really hard off the pitch. He is definitely the top one.
I'm having a Gretar time: Steinsson is enjoying life with Bolton
'When I came on trial some years ago I told stories about him when I returned home because I had met a lunatic who trained more than me and still does. I really respect him and there is no sign of him stopping.'
Steinsson, who intends to treat the match like any other on the road, is having the time of his life.
Bolton go into the game on the back of a 3-0 win against West Ham and he said: 'We've got goals in us. We tend to go for it. The players like the ideas of the manager (Owen Coyle).
'It is high energy and really exciting as you never know what is going to happen. 'We know it is a big occasion but for foreign players who have been playing around Europe, like myself, we will prepare like we do for any other away game.'
Steinsson believes Stoke are a much better team than they are given credit for. He added: 'People talk about them in terms of throw-ins, free-kicks and corners but they have some good footballers.
'Both teams have done brilliantly and it will be a really even, exciting game as there are lot of experienced players around.'
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