Jaaskelainen was required for the final period of the match after Adrian had been sent off for handling outside the area.
It was a rare situation even for a goalkeeper of Jaaskelainen's experience, and the Finnish stopper admits he was shocked that nerves affected him.
"That's just the second time in my career I've come on from the bench," he said.
"You just need to keep focused on the bench and it did come as a surprise on Wednesday because you never expect that to happen.
"I was surprised with the experience I have that I was nervous for the first couple of minutes. But that got better later in the game."
Despite Jaaskelainen saying that he was anxious, it certainly wasn't evident in his performance as he looked a picture of calm.
The 39-year-old managed to pull off a couple of notable saves to preserve his side's clean sheet and help them claim what was an impressive point at St. Mary's.
It was a performance that proved that he still has something to offer the side, despite his advancing years, and he will be looking to ensure that his standards do not dip in the coming weeks.
Jaaskelainen has still not started a Premier League match this season, but he should be in the team next time out, with Adrian suspended, and will delighted if he can make it two clean sheets out of two.