En route to the Tigers' World Series berth, Stevenson attracted media attention with an outstanding defensive play in center field.

Playing behind starting pitcher Jared Poche, Stevenson leaped toward the warning track and laid out to take away a likely RBI extra-base hit from the University of North Carolina Wilmington's designated hitter.

[15] After Lucas Giolito, Reynaldo Lopez and Dane Dunning were traded to the Chicago White Sox in December 2016,[16] Stevenson ranked as the Nationals' fifth-best prospect, according to MLB.com.

[23] He made his major league debut the same day, pinch-hitting and coming in on a double switch in the sixth inning to play left field.

[24] The following month, on August 10, he made a diving catch down the left field line to take away an RBI and extra bases from Miami Marlins second baseman Dee Gordon with two outs in the top of the ninth, preserving a 3–2 lead in the game as Nationals closer Sean Doolittle locked down the save.

[25] On August 27, Stevenson recorded his first major league RBI with a go-ahead, bases-loaded walk against the New York Mets that gave the Nationals a 5-4 victory.

[26][27] On August 28, the Nationals optioned Stevenson back to Syracuse following the return of left fielder Jayson Werth from the disabled list.

[31] Stevenson entered a game on April 25 against the San Francisco Giants at AT&T Park with only 10 major-league hits and two major-league RBIs in his career, but, playing in left field that day, he went 4-for-5 from the plate with two doubles and a walk and scored two runs as part of a Nationals offensive explosion that ended in a 15–2 Washington victory.

[34] 2019 would also see him make his postseason debut: pinch-running for Ryan Zimmerman in the 8th inning of the Wild Card Game against the Milwaukee Brewers, he would score the tying run on Juan Soto’s single; acting aggressively due to Stevenson’s speed, Brewers right fielder Trent Grisham misplayed the ball, allowing the eventual winning run to score as well.

While not on the playoff roster for the rest of the Nationals’ championship run, Stevenson would take the field before Game 3 of the World Series to catch the ceremonial first pitch from Apollo 11 astronaut Buzz Aldrin.

[37] He appeared in 135 games for the Triple-A Rochester Red Wings, slashing .279/.344/.457 with 16 home runs, 67 RBI, and 39 stolen bases.

[44] Stevenson was described by Nationals general manager Mike Rizzo after being drafted in 2015 as someone who "plays 100 mph with his hair on fire", a phrase he has also applied to standout players like Bryce Harper[45] and Adam Eaton.