Writing on Twitter, and in an interview with tabloid Aftonbladet, Knutson says that he has information that Nuder will be the first they call.
Pär Nuder has already said he doesn't want to be party leader, but analysts say if he has wide support within the party it will be hard for him to say no.
Social Democrat representatives from across Sweden are currently delivering a "wish list" about what qualities a new party leader should have and what the priorities should be in selecting Mona Sahlin's successor.
Aftonbladet's political commentator Lena Melin says she wouldn't be surprised if Nuder was their final choice, but that she is surprised that there seem to be two parallel selection processes going on within the party.
Current leader Mona Sahlin is stepping down due to last year's catastrophic election result. The Social Democrats are currently in the middle of a renewal process, with working groups discussing what went wrong in the last election, and how their policies need to change to attract more voters, especially from urban areas.
For a long time it seemed a priority was to get new blood in the party leadership, something that now seems to have become less important. Pär Nuder was a minister in the last Social Democrat government, and was Prime Minister Göran Persson's right-hand-man, something which left him open to widespread criticism both inside and outside the party. He was removed from the shadow cabinet several years ago and is not currently politically active.
Other names previously tipped for the top job are Veronica Palm, the Social Democrats' tax spokesperson, and Sven-Erik Österberg, the man in charge of the party's parliamentary group.