Mattocks, 28, scored 10 goals, tied for second on the team, but was relegated to reserve duty after Rooney’s high-impact signing in the summer. He never fully took to the backup role and seemed set on pursuing other opportunities this winter. Mattocks is eligible for MLS’s reentry draft next month.

“He was pretty clear he wanted to play regularly,” Kasper said. “With Wayne here, it was always going to be hard for him to get onto the field."

Mattocks is among several players not returning next season. United announced Wednesday that it has declined contract options on three regulars (Yamil Asad, Nick DeLeon and Kofi Opare) and six reserves (Ian Harkes, Vytautas Andriuskevicius, Kevin Ellis, Jared Jeffrey, Dane Kelly and Bruno Miranda).

Asad, however, seems likely to stay. United is fine with the terms of the contract, but in order to retain him, the club must exercise a transfer option with Argentine club Velez Sarsfield. Terms of such transactions are typically subject to negotiation. Asad has been on loan in MLS since joining Atlanta in 2017.

Kasper said he is optimistic the sides will strike a deal but cautioned that it would “take time,” meaning Asad (nine goals, eight assists) might arrive late to training camp, which is scheduled to open Jan. 21.

At seven seasons, DeLeon boasts the longest continuous service with United, but after missing four months with a knee injury that left him with a bone-on-bone issue, the organization wants to renegotiate his contract at a lower rate. He earned $275,000 this year.

The sides have been talking and DeLeon would like to return, Kasper said.

Opare started 10 times in central defense but missed the last portion of the year with a foot injury that required surgery. He also underwent a hernia operation recently. Kasper said the club will reevaluate him in January before deciding whether to extend a new offer.

Harkes, the second-year homegrown midfielder from Fairfax, saw a dramatic drop in playing time this season after the arrival of several players. He is seeking a fresh chance elsewhere in MLS or overseas.

United could have retained Harkes’s MLS rights by offering him a new deal, but “if there is an opportunity for him, we’re not going to stand in his way,” Kasper said. “We feel he needs to go somewhere where he plays 30-plus matches.”

United was willing to trade him this past summer, Kasper said, but nothing materialized.

The club has not ruled out re-signing Ellis, a defender who arrived in September, and Jeffrey, a seldom-used defensive midfielder.

In addition, third-choice goalkeeper Travis Worra is a free agent seeking opportunities elsewhere — Kasper said he is looking abroad — and defender Taylor Kemp retired this month because of injuries.

David Ousted, the backup goalkeeper behind Bill Hamid, is under contract next year but might not return. “There have been some teams that have reached out,” Kasper said.

Oniel Fisher, a revelation at right back before suffering a serious knee injury late in the year, is a free agent as well, but United is seeking to re-sign him. He probably would not be healthy again until the summer.

As expected, United exercised a contract option to keep Argentine midfielder Luciano Acosta, who enjoyed a breakout season partnering with Rooney. He was named to MLS’s Best XI (all-league team). The club also plans to open negotiations with Acosta on a long-term deal.

United also exercised an option on homegrown defender Jalen Robinson.

Another homegrown player, 18-year-old midfielder Chris Durkin, has attracted interest overseas. Kasper said European clubs have reached out but not made any formal offers.

“He had a great year and the future is really bright for Chris,” Kasper said. “The challenge for us next year is, can we get him on the field? Where does he fit in so we can continue pushing his minutes and growth?”

Durkin started 16 times but was behind Russell Canouse and Junior Moreno on the defensive-midfield depth chart.

With Mattocks leaving, Kasper said, acquiring a backup for Rooney at striker has become a high priority. The search, he added, will include domestic and international candidates.

United’s other priorities are central defense and right back, where there is no clear-cut starter while Fisher recovers and the club engages in talks with DeLeon. Paul Arriola, a wide midfielder, filled in at times this season.

Kasper said the team will also pursue depth in central midfield, left back and goalkeeper. United, he added, will also try to acquire young international attackers to develop.

It’s unclear whether United would attempt to sign a third designated player; Rooney and Arriola fill two of the maximum three high-salary slots. A new contract for Acosta could make him a designated player, although United would probably opt to apply targeted allocation money to soften the impact and leave a DP slot open.

In other news:

United has hired Dane Murphy as technical director, a position under Kasper to identify players, oversee the roster at Loudoun United — D.C.'s second-division squad — and strengthen the connection between the club and youth academy.

Murphy, a University of Virginia standout who played for United in 2008, left a similar position with Real Salt Lake. He is currently scouting for United in Central America.

Kasper said that, with Loudoun United serving as a development option, United will be “more aggressive than in the past signing homegrown players. I would say we are hoping to sign a few this winter.”

He wouldn’t comment on any potential targets, but University of Maryland junior defender Donovan Pines (Clarksville, Md.) seems high on the list and academy forward Griffin Yow (Clifton, Va.) was named last week to the U.S. under-17 national team.

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Players under contract

Goalkeepers: Bill Hamid, David Ousted.

Defenders: Steve Birnbaum, Frederic Brillant, Joseph Mora, Chris Odoi-Atsem, Jalen Robinson.

Midfielders: Luciano Acosta, Paul Arriola, Russell Canouse, Chris Durkin, Junior Moreno, Ulises Segura, Zoltan Stieber.

Forwards: Wayne Rooney.

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