SEATTLE — What was known was that Mauro Rosales would be leaving Sounders FC.

What wasn’t known was that the team would be receiving something in return.

Seattle’s busy offseason continued Wednesday as Rosales, a 32-year-old midfielder, was traded to Chivas USA for the rights to young forward Tristan Bowen and the valuable No. 2 spot in the allocation order. Chivas moves down to the No. 13 spot in the allocation order, the mechanism from which returning U.S. national team players rejoin MLS.

The Sounders have acquired standouts like Kasey Keller and Eddie Johnson via the allocation order and could use the high position to add another key player.

Additions will be needed to help make up for Rosales’ production. The designated player had led the team in assists the past three seasons, 34 overall, tied for the franchise record with Fredy Montero.

Seattle had declined a contract option on Rosales following the season, and the veteran was set to take part in the upcoming MLS Re-Entry Draft starting Thursday, meaning Seattle would have received no compensation.

Sounders officials indicated financial constraints ultimately led to the breakup.

“Mauro has been an important part of our organization, both on and off the field, for the past three years,” said Adrian Hanauer, part-owner and general manager, in a news release. “It will be difficult to see him leave, but our salary-cap situation made this decision necessary.”

Coach Sigi Schmid noted finances particularly came to the forefront when the team signed Osvaldo Alonso to a DP contract, giving the team a full allotment along with Clint Dempsey and Obafemi Martins.

“We could only have three DPs,” said Schmid, “so you have to make a decision there when a player wants to continue to make that salary. It forces your hand.”

Rosales had been Seattle’s primary captain the past two seasons, and his average of 0.50 assists per 90 minutes ranks fifth-best in league history (minimum 20 assists).

Bowen, 22, still needs to come to terms with the Sounders. He signed with MLS five years ago as a homegrown player with the Los Angeles Galaxy and played the past three seasons with Chivas USA, setting career highs in 2013 with 22 appearances and 15 starts.