Complex sentence: From 1937 until his retirement in 1948 Smith was a star pitcher on the Monarchs, possessing what may have been the best curveball in baseball history; but he was overshadowed by his more flamboyant teammate Satchel Paige.
Split into simpler sentences: From 1937 until his retirement in 1948 Smith was a star pitcher on the Monarchs. He possessed an outstanding curveball, but he was overshadowed by his more flamboyant teammate Satchel Paige.