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Will Ferrell just got his first vote of confidence as an MLS owner ... by a U.S. Soccer star who says Ferrell's love for the sport is legit ... and just what the league needs.

We got Sean Johnson out at LAX ... a goalkeeper for the Chicago Fire of the MLS and a member of team USA ... and asked him about Will joining the ownership group of the new soccer franchise in L.A.

Check out the clip -- Johnson is obviously stoked about Ferrell ... saying big stars like Will and Seattle Sounders owner Drew Carey are just the type of high-profile attention the league needs.