The Cubs are one of the three major league teams that did not participate in the nationwide COVID-19 antibody study being concluded this week by researchers at Stanford and USC, according to sources Thursday.

But the sources said the Cubs, who did not resolve discussions with their medical staff over details of the testing in time to consent, expect “the opportunity to be included in Phase II” of the project.

It was not immediately clear what that phase would involve or when.

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The Toronto Blue Jays also did not participate in the testing, a source said, because they are not a U.S. team. The other U.S. team that did not participate was not immediately known.

In an effort to secure widespread testing across multiple demographics and regions and achieve quick results, researchers seeking to determine national rates of infections (including those who may have recovered and developed immunity), approached Major League Baseball.

One of the researchers in the study, Dr. Daniel Eichner, is the president of the Sports Medicine Research and Testing Laboratory, which has a relationship with MLB through its drug-testing program.

Eichner told several media outlets in recent days that such a widespread study — involving 10,000 tests with results collected this week — might have otherwise taken months to set up through normal academic methods, and he said the league responded immediately in support of the project.

The study, which reportedly included finger pin-pricks of owners, executives, players and swaths of employees that reached to vendors, is unrelated to MLB’s efforts to start an abbreviated season at some point, Eichner stressed.