Steven Souza Jr. in spring training. (Photo by John McDonnell/The Washington Post) Steven Souza Jr. in spring training. (Photo by John McDonnell/The Washington Post)

The Nationals’ Class AAA affiliate, the Syracuse Chiefs, has been one of the organization’s best teams and four key players were named International League all-stars for their roles.

Outfielder Steven Souza Jr., catcher Jhonatan Solano and pitchers Taylor Hill and Aaron Laffey were selected as all-stars Wednesday, all for the first time. In the midst of strong seasons at Syracuse, Souza and Hill made their major-league debuts.

Souza, 25, has been one of the most interesting developments of the season. He has improved at every level of the minor leagues and impressed at big league camp this spring. Souza took an even bigger step this season.

In his first season at Syracuse, Souza has been an offensive force. He leads the International League in batting (.354), on-base percentage (.438) and slugging (.586). His OPS (1.025) is by far the best in the league, ahead of Pirates’ recently promoted super-prospect Gregory Polanco (.945).

Souza also has 13 home runs and 49 RBI along with 15 stolen bases. Entering Wednesday’s games, he averaged a home run every 17.85 at-bats. He has spent the majority of the season playing right field but also has played center.

Solano, 28, is having his best minor league season. The one-time Nationals backup catcher is hitting .265 with a .424 slugging percentage and a career-best nine home runs and 41 RBI. He also has guided a Syracuse pitching staff that has endured several injuries yet still has the league’s second-best team ERA (3.38).

Hill, 25, made his major league debut last week when the Nationals needed a fresh bullpen arm. At Syracuse, he has continued his quiet dominance. He is 9-2 with a 1.90 ERA and stellar 6.8 K/BB ratio over 99 2/3 innings. Laffey, 29, added in late March as pitching depth, leads the International League with 10 wins and also sports a 2.93 ERA over 92 innings.

Zach Walters and Tyler Moore also are posting fine seasons at Syracuse but played significantly less than others because of major-league stints. Walters has a .260 average, .880 OPS and 11 home runs. Moore is hitting .340 with a .982 OPS with as many walks (17) as strikeouts (21).

Emmanuel Burriss, a D.C. native, is hitting .294. Brandon Laird, acquired in a minor league trade in the spring, is hitting .309 with a .821 OPS and seven home runs. Several players have spoken highly of the work of Joe Dillon, who is in his first year as Syracuse’s hitting coach.

The all-star game will be held July 16 in Durham, North Carolina and air on MLB Network.

>>> In other Syracuse news, Greg Dobbs has accepted his outright assignment to the Chiefs. He was designated for assignment by the Nationals last week.