First Base: Jim Thome 48.0 WAR
This seems pretty obvious as Jim Thome's WAR total in Cleveland is sixth all-time among hitters in team history. The long time first baseman appeared in 1,399 games in Cleveland, hitting 337 home runs with a .980 OPS with back-to-back seventh place American League MVP finishes in his final two years with the team.
Second Base: Nap Lajoie 79.6 WAR
The former namesake of the team and all-time WAR leader, Nap Lajoie, would be at second. From 1902 to 1914, Lajoie had over 2,000 hits, 400 doubles, and a near .340 batting average. Lajoie led all of baseball in hits and doubles in 1904 (208, 49), 1906 (214, 48), and 1910 (227, 51) with Cleveland.
Third Base: Jose Ramirez 42.4 WAR
There is still a lot of time left in the career of Jose Ramirez, but he is already the Guardians' franchise leader in WAR for a third-baseman. A few more years of Ramirez performing at a level receiving MVP votes should see him catapult into the Top-5 all-time.
Shorstop: Lou Boudreau 61.8 WAR
Third in team history and leading all shortstops is Lou Boudreau. From 1938 to 1950 Boudreau was manning shortstop, leading all of baseball with 45 doubles twice (1941, 1947) and the American League in 1944 with 45. Boudreau had many Top-10 MVP finishes, including being named American League MVP in 1948 en route to Cleveland's last World Series title.