Fredy Montero hasn’t played for the Sounders since the end of the 2012 season, but his tenure with the team didn’t officially end until Thursday.

The forward has been transferred to Sporting Lisbon, the Portuguese team he has been playing for on loan since July. An option to buy was part of the loan agreement, which came after Montero played six months for Colombia’s Millonarios.

The Sounders received a transfer fee for Montero, but an amount wasn’t specified in the news release. Sporting Lisbon documentation indicated the move could cost up to $4.5 million.

“Fredy has been and will always be a special member of our family,” said Adrian Hanauer, Sounders FC part owner and general manager, in the release. “Fredy had a wonderful career in Seattle and is continuing that success overseas. Hopefully his quality of play gives him an opportunity to be added to the Colombia World Cup roster. We wish him well with this next chapter of his career.”

Montero is Seattle’s all-time leading scorer with 47 MLS goals, 60 when including the U.S. Open Cup and CONCACAF Champions League. His high-scoring ways continued in Portugal, where he has a league-leading 13 goals (he has 19 goals in 20 games including nonleague competition).

Sporting Lisbon listed Montero’s buyout clause at 60 million euros, about $81.3 million.

Joshua Mayers: 206-464-3184 or jmayers@seattletimes.com