With playoff spots still wide open, we pinpoint the key players to watch down the stretch, like Yankees rookie shortstop George Lombard Jr.

St. Louis Cardinals outfielder Joshua Báez had arguably the best debut in baseball history on Saturday afternoon at Wrigley Field. He went 3 for 4 with three home runs, all in his first three at-bats, including a monster 449-foot blast to center field on the very first pitch he saw as a big leaguer.