WASHINGTON, D.C. -- There were only a few questions left to be answered about the Nationals¡¯ 26-man roster by the end of Spring Training. Then, four positive COVID-19 test results, five subsequent contact-tracing quarantines on the big league roster and an injury rendered 10 players unavailable for their season opener on Tuesday against the Braves.

Catchers Alex Avila and Yan Gomes, first baseman Josh Bell, infielders Josh Harrison and Jordy Mercer, left fielder Kyle Schwarber, starting left-handers Patrick Corbin and Jon Lester and southpaw reliever Brad Hand were placed on the injured list due to COVID-19 protocols. Additionally, right-handed reliever Will Harris was placed on the 10-day injured list (retroactive to March 29) because of right hand inflammation.

The Nats¡¯ 2021 Opening Day roster includes two catchers, six infielders, five outfielders and 13 pitchers (three starters, 10 relievers). To complete the roster, catcher Tres Barrera, infielders Luis Garc¨ªa and Carter Kieboom, outfielder Yadiel Hernandez and right-handers Sam Clay, Ryne Harper and Kyle McGowin were recalled; the contract of catcher Jonathan Lucroy was selected; and outfielder Cody Wilson was selected as a replacement player.

Catchers (2): Jonathan Lucroy, Tres Barrera
Not only did the Nationals add Lucroy to their Major League roster on Tuesday, they tabbed him to catch Opening Day starter Max Scherzer. Lucroy is entering his 12th season, after playing for the Red Sox in 2020 and going through Spring Training this year with the White Sox. Barrera is the Nats¡¯ No. 19 prospect, per MLB Pipeline. He's appeared in two big league games, and he is returning from missing all of last season because of an 80-game suspension after testing positive for a PED in July 2020.

First base (1): Ryan Zimmerman
The plan is for Bell to start at first base for the majority of the games this season. Until he comes off the IL, the veteran Zimmerman will man the position.

¡°I can play every day for the short-term -- I¡¯m still capable of doing that,¡± Zimmerman said on Monday. ¡°And I think [manager] Dave [Martinez is] smart about that as well. He¡¯s not going to run me into the ground the first however many days of the season.¡±

Zimmerman, who elected not to play in 2020 because of concerns about the pandemic, belted six homers in 10 Spring Training games this year.

Second base (2): Luis Garc¨ªa, Carter Kieboom
Hern¨¢n P¨¦rez got the start on Opening Day against left-hander Drew Smyly, but Garc¨ªa is likely to get starts while Harrison is on the IL. Last year, Garc¨ªa stepped in when Starlin Castro suffered a season-ending right wrist injury and made 35 starts at second. With Castro shifting to the hot corner, Kieboom has been working out at second base, where he started 41 games in the Minor Leagues.

Third base (1): Starlin Castro
The starting job was Kieboom¡¯s to earn this spring, but the Nats decided to go with the veteran Castro, who played 45 games at the hot corner for the Marlins in 2019.

Shortstop (1): Trea Turner
Shortstop is one of the Nats¡¯ strongest positions thanks to the standout play of Turner. Last season, Turner led the Majors with 78 hits and led all shortstops in batting average (.335), on-base percentage (.394), slugging percentage (.588), OPS (.982) and extra-base hits (31). He finished seventh in National League MVP Award voting.

Outfield (5): Juan Soto, Victor Robles, Andrew Stevenson, Yadiel Hernandez, Cody Wilson
Andrew Stevenson emerged as the top candidate for the fourth outfield spot, and he will man left field while Schwarber is on the IL to round out the outfield with Soto (right) and Robles (center). Hernandez can be called on to play right or left, and both he and Wilson made impressions in Spring Training with their speed.

Utility (1):Hernán Pérez
The veteran P¨¦rez was added to the Major League roster after a strong spring performance. His versatility includes the ability to play second (see above), third and the outfield (see above). He's also emerged as an option for an emergency catcher.

Starting pitchers (3): Max Scherzer, Stephen Strasburg, Joe Ross
The Nationals starting rotation took a hit when left-handers Corbin and Lester were placed on the IL. To fill the vacancies, the Nats could call on Erick Fedde and Austin Voth, both of whom have experience starting, or use an opener in Kyle McGowin or Luis Avil¨¢n. Martinez also will be mindful of the limited innings Strasburg (five) and Joe Ross (elected not to play) threw in 2020.

Relievers (10): Daniel Hudson, Tanner Rainey, Wander Suero, Kyle Finnegan, Erick Fedde, Austin Voth, Luis Avilán, Sam Clay, Kyle McGowin, Ryne Harper
The Nationals¡¯ bullpen is built for depth. Fedde and Voth, who contended for the fifth starting spot, can throw multiple innings. Avil¨¢n and Suero also can get more than three outs. The Nats will look to Brad Hand as the closer and call on Harris, Daniel Hudson and Tanner Rainey for late innings. (Harris is seeking further medical attention after experiencing numbness in his right fingers; a venogram ruled out a blood clot.) Martinez said on Sunday, ¡°We're confident with the guys that we're going to keep [that] they can get the job done."