The 1948 SMU Mustangs football team represented the SMU Mustangs of Southern Methodist University during the 1948 college football season. Doak Walker was a junior when he won the Heisman Trophy. Doak established several other Southwest Conference records that still stand. Using only the above description and what you know about the world, "Walker began his career as a freshman" is definitely correct, incorrect, or inconclusive? 