Getty Images

Major League Baseball's owner-imposed lockout was lifted on Thursday, some 99 days after it was first implemented. Opening Day, once scheduled for March 31, will instead occur a week later, on April 7. While that news understandably won the day in headlines, there was another development that will have a direct impact on MLB's upcoming regular season; that's because some players may find themselves on the sidelines whenever their teams head to Toronto to take on the Blue Jays.

According to Boston television anchor Duke Castiglione, the new Collective Bargaining Agreement mandates that players who haven't received their COVID-19 vaccinations will not be allowed to play games in Canada. Those players will instead be placed on the restricted list, meaning they won't receive payment or service time for the games they miss.

Shi Davidi and Ben Nicholson Smith of Sportsnet add that "a few teams" took "serious issue" with the ruling before relenting. Davidi also tweeted that 88 percent of MLB's "tier 1" individuals -- that is, players, coaches, trainers, and others -- were fully vaccinated by the end of the postseason. It's unclear if MLB has updated its policies to redefine "fully vaccinated" as having received three shots, including a booster.

Back in January, MLB stepped away from plans to require COVID-19 vaccinations for all minor-league players. Those who work with the players, like coaches and trainers, are required to have up-to-date vaccination records.

It's worth noting that seven teams were below MLB's 85 percent vaccination threshold as of last September. Teams who met that mark were allowed to loosen restrictions on masking and other activities. Interestingly, according to The Athletic's Ken Rosenthal, that group of seven included both the Boston Red Sox and the Seattle Mariners, two teams who could end up jockeying for a playoff spot with the Blue Jays.

It's not apparent which players on those clubs were or remain unvaccinated, but it could end up costing them and their teams if and when the schedule calls for a trip to Toronto.