Mahtook hit .356 in September, which was the second-highest average ever posted by a Rays rookie in a calendar month, trailing Rocco Baldelli in April 2003 (.368).
Included in Mahtook's September run were five home runs in his final 23 at-bats and on Sept. 18 against the Orioles, he set a Rays rookie record with five hits, going 5-for-5 with two doubles.
September "was the best I've ever felt as a professional," Mahtook said. "I've had some stretches in '14 in Triple-A, I felt good pretty much the entire year. But September last year was probably the hottest I've been and the most consistent my swing has felt.