A Cincinnati Reds player tested positive for COVID-19 on Friday, jeopardizing the team's game Saturday against the Pittsburgh Pirates and reigniting fear of another outbreak in the sport after a pair of outbreaks severely affected the opening weeks of the season, sources told ESPN.

The teams were informed of the positive test after their game in Cincinnati on Friday. The reported positive came on the eve of the St. Louis Cardinals, who have not played since July 29, returning to the field against the Chicago Cubs.

The Athletic first reported that a Reds player had tested positive.

Outside of St. Louis, Major League Baseball had reported no positive tests in the previous two weeks, leading to hopes in the sport that after the outbreaks among the Cardinals and, earlier in the season, the Miami Marlins, that the sport could find a period of calm.

That won't be the case over the next few days, as the Reds begin the contact-tracing process and potentially isolate players who came into contact with the infected player.

Multiple times have the Reds feared COVID-19 issues, only for them to be unfounded. Third baseman Mike Moustakas and outfielder Nick Senzel self-reported symptoms and spent days on the injured list before negative tests allowed them to be reinstated. First baseman Joey Votto spent one day on the IL before returning. And while infielder Matt Davidson tested positive, follow-up tests were negative, leading to the belief his first result was a false positive.

The Reds are likely to undergo increased testing beyond the standard every-other-day saliva test, and with the incubation period for the virus believed to be between two and 10 days, the likely postponement of Saturday's game could extend to Sunday and even beyond, sources said.

MLB's deepest concern regards potential team-to-team transmission. No positive cases of on-field transmission showed up on the Philadelphia Phillies following their July series against the Marlins, nor on the Minnesota Twins, who last played the Cardinals. The Pirates might be subject to increased testing nevertheless.

The Reds, a trendy preseason playoff pick, moved to 9-11 with an 8-1 victory against the Pirates on Friday.