Marcus Peters was the best player in a secondary that finished 9th in the country in pass yards per attempt allowed at just 6.0. Despite the loss of first round NFL draft pick Desmond Trufant at the opposite corner, from 2012 to 2013 that number dropped more than a half a yard per attempt.
Peters wasn't just a key member of a defense that was exceptional -- his individual statistics were phenomenal as well. He registered 55 total tackles, 3.5 tackles for loss, a sack, five interceptions, nine breakups, a fumble forced and a fumble recovered. His 14 passes defensed tied him for the most in the conference. He was 3rd in breakups and 5th in interceptions. Counting only conference games, Peters had two more passes defensed than any other Pac-12 player.
In individual matchups Peters has been a star as well. The last two Biletnikoff Award winners have lineup up against 21, and their results were not pretty. In 2012 Marqise Lee was held to both his lowest catch total (2) and lowest receiving yardage total (32) against the Huskies. A season ago Brandin Cooks notched 10 catches for 110 yards and a touchdown, but a good chunk of that came well after the Husky starters had retired for the evening, and Peters was perhaps the best player on the field all night as he intercepted two passes, broke up three more, and forced a fumble (which he recovered).
Marcus Peters is a legitimate star in college football. There may be other corners in the country that you can say might be as good as him, but you cannot find one who you can say is clearly better. If you're going to replace three fourths of your secondary, having Marcus Peters as the one guy coming back is about as good as you could wish for.