We all get old and slow down but the fact of the matter, Tom Brady never had the speed even when he was 20. He said as much in a interviews way back in the day. I've seen him state it when he was in High School. So, yeah, he is getting older but even if he were 20 years old...he never would have made that play on Robert Alford.
From what I’ve read and seen he’s probably in better shape today than when he was drafted in the sixth round.