The Sweden international has barely featured for the Hornets, though says he is a better player for the experience.
He said, "I have become a better goalkeeper since I left, absolutely. I have still trained with very good players day in and day out in the world's best league. I have become more quick-thinking and got into that pace.
"The club (Hacken) showed great interest and it felt right for me. There are several national team gatherings soon and a European Championship play-off next summer that I want to be part of and compete for."