Nolan spent 10 years playing with Jaaskelainen at Bolton and he believes the Hammers have signed a top-class replacement for the departed Robert Green.
Speaking to West Ham TV Nolan said, “Obviously Jussi’s record speaks for itself.
“When we were at Bolton and were at our height finishing in the top-eight in four straight seasons, he was probably easily worth 12 points a season to us and that was just in games that he won for us on his own by pulling off saves when our backs were against the wall.
“He is that type of keeper who can pull of great saves. He is a good lad to have around the place too.
“There was no-one more disappointed than me to see Rob Green go. I was close to him and consider him a good friend and we’ve stayed in touch. I wish him well in his move but was disappointed not to see him stay because it would have been interesting to see those two going at it for the No1 jersey.
“Jussi is someone the gaffer knows really well and I’m sure he’ll warm the West Ham fans’ hearts quickly because he is that type of player and character.”