Veteran first baseman Ryan Zimmerman and starting pitcher Joe Ross of the Washington Nationals were among the first major leaguers to opt out of the 2020 season because of concerns about the novel coronavirus — although with players due to begin reporting for mandatory virus testing this week ahead of Friday’s opening of “summer camps,” they almost certainly will not be the last.

The announcements from Arizona Diamondbacks pitcher Mike Leake, then Ross and Zimmerman — none of whom are known to have medical concerns that would qualify them as high-risk, which would ensure they still are paid for 2020 — came in a span of several hours Monday afternoon and reflected concern among some players that the risk of playing baseball amid a global pandemic may not outweigh the rewards in all cases.

“After a great deal of thought and given my family circumstances — three young children, including a newborn, and a mother at high risk — I have decided not to participate in the 2020 season,” Zimmerman, 35, said in a statement Monday. “… I cannot speak for anyone else, but given the unusual nature of the season, this is the best decision for my family, and I truly appreciate the [Nationals’] understanding and support.”

The Nationals also released a statement from General Manager Mike Rizzo, confirming that Zimmerman and Ross opted out “for the personal health and safety of themselves and their loved ones.” The Nationals, Rizzo said, “are one hundred percent supportive of their decision not to play this year.”

The 2020 season, then, will be the first in the history of the Nationals that won’t include Zimmerman, long considered the face of the franchise. He joined the Nationals in 2005, their first season in Washington after they relocated from Montreal, and went on to earn more than $137 million in total salary through 2019, making two all-star teams and starting all seven games at first base in the 2019 World Series, when the Nationals beat the Houston Astros for the franchise’s first championship.

Zimmerman signed a one-year, $2 million contract with the Nationals this past winter for what was presumed to be a farewell season, but in his statement Monday he said he was not ruling out playing in 2021.

“To be clear, I am not retiring at this time,” Zimmerman’s statement said. “I have not decided on my future in baseball past 2020. But this year, I’ll be staying safe at home and pulling as hard as anyone for the guys to defend our championship.”

Baseball is bracing for an unknown number of opt-outs this week as the opening of camps draws near. Under the terms of the health and safety agreement struck by Major League Baseball and its players’ union last week, only those players deemed high-risk — because of preexisting medical conditions that would make them vulnerable to the coronavirus — will receive their salaries and service time if they opt out.

Zimmerman’s decision was not surprising, given the reluctance he expressed in an entry he wrote last week for a weekly diary he has been keeping for the Associated Press.

“I don’t think there’s a right or wrong answer; it’s everybody’s individual choice,” he wrote. “At the end of the day, does a player feel comfortable going to the field every day — and in my case, more importantly — feel comfortable coming home every day and feel like they’re not putting anyone else in danger?”

Zimmerman’s $2 million salary for 2020 was due to be prorated to $740,740 for the 60-game season under the terms of the March agreement between MLB and the players’ union over salaries.

Ross, 27, was the leading contender for the Nationals’ fifth starter job this season, and he would have earned $555,555 — prorated from his original salary of $1.5 million. More importantly, he will accrue no service time this season, which will delay his free agency beyond 2022, when he was due to be eligible for the first time.

Leake, 32, stands to lose the most in terms of salary; he was originally due to earn $16 million this season, or around $5.5 million in prorated salary for the 60-game season. Leake’s contract also contains a mutual option for $18 million in 2021, which would result in a $5 million buyout if it is not exercised.

Because they were on major league contracts, the three players received $286,500 apiece out of a total pool of $170 million in advanced salaries covering April and May, stemming from the March agreement.

“During this global pandemic, Mike and his family had many discussions about playing this season,” Leake’s agent, Danny Horwits, said in a statement. “They took countless factors into consideration, many of which are personal to him and his family. After thorough consideration, he has chosen to opt out of playing in 2020. This was not an easy decision for Mike. He wishes the best of luck and health to his Diamondbacks teammates this season and he’s looking forward to 2021.”

Jesse Dougherty contributed to this report.