Washington Spirit captain Andi Sullivan will undergo surgery Thursday after tearing the medial meniscus in her left knee, an injury that will sideline her for the remainder of the NWSL’s Challenge Cup and three to six months overall.

Sullivan, a U.S. national team midfielder, was hurt in the second half of Sunday’s 1-0 victory over the Houston Dash in Herriman, Utah. An MRI exam revealed the injury, which is to the same knee that required ACL surgery in late 2016 while she starred at Stanford.

“I’m obviously disappointed to not be out there playing, but I’m excited to watch the rest of the tournament and I’m hoping to see my team win it all in the end,” she said in a statement distributed by the Spirit. “I’m hopeful that I can continue to build off of the performances I had in the Challenge Cup after I complete rehab in a few months, and I’m confident that I will come back from this injury stronger.”

Spirit Coach Richie Burke said: “I’m coming to terms with losing such an influential player for the tournament, but my main thoughts are with Andi and her rehabilitation process. ... The team is rallying around our captain and incredible leader, and we are now highly motivated to play extra hard in her honor.”

Sullivan is aiming to return in time for a proposed U.S. national team training camp in January.

The NWSL is not expected to conduct a regular season this year. The league is planning to hold a board meeting next week to begin charting a course amid the novel coronavirus pandemic.

The loss of Sullivan comes as the Spirit expects to welcome back midfielders Rose Lavelle (ankle) and Jordan DiBiasi (hip). Both missed the Houston match.

Lavelle trained the past two days and is expected to play, and DiBiasi should be ready after resting for a few days, Burke said.

The injury came in the Spirit’s final match of the preliminary round. Washington (2-1-1) will be the No. 2 seed in the knockout stage and face Sky Blue FC (1-2-1) on Saturday at 12:30 p.m. ET. The other Saturday match pits No. 3 OL Reign (1-1-2) against the No. 6 Chicago Red Stars (1-2-1) at 10 p.m.

On Friday, the top-seeded North Carolina Courage (4-0-0) will face the No. 8 Portland Thorns (0-1-2) at 12:30 and the No. 4 Dash (1-2-1) will play the No. 5 Utah Royals (1-2-1).

All quarterfinals and the July 22 semifinals will appear on CBS All Access, a digital pay platform. CBS national network will carry the July 26 final.