NFL Nation reporter Mike Rodak assesses which rookies on the Buffalo Bills could earn a starting berth this season.

Why John Miller could start: Rex Ryan came right out and said it this spring: the Bills drafted Miller with the intention of starting him at guard. When Miller was selected in the third round in May, my initial thought was that he would slide into a reserve role behind Richie Incognito and Chris Williams, but Williams' offseason back surgery and absence from offseason practices have given Miller the inside track to starting. Coaches have raved about his football intelligence, but he'll have a tough task ahead of him this summer when he'll have to hold his ground against Pro Bowl defensive tackles Kyle Williams and Marcell Dareus. That will be good preparation for possible assignments this season against Miami's Ndamukong Suh and the New York Jets' Sheldon Richardson.

Why Nick O'Leary could start: Offensive coordinator has indicated that he could dress as many as four tight ends on game days, giving O'Leary an opportunity to work into the offensive mix. He won't start over Charles Clay but could join Clay on the field in certain situations. O'Leary is undersized but offers some pass-catching ability against short zones and down the seams. The competition behind Clay is wide open this summer between O'Leary, Chris Gragg, MarQueis Gray and undrafted rookie Clay Burton. The unsettled depth chart and Roman's usage of tight ends gives O'Leary the best chance to "start" among rookies other than Miller.

Why Ronald Darby could start: In an ideal world, the Bills will have Darby learn from veteran defensive backs coach Donnie Henderson this season before giving him a larger role next season, when Leodis McKelvin's salary-cap hit and the Bills' lack of salary-cap space makes McKelvin a logical candidate to be released. McKelvin and fellow starter Stephon Gilmore haven't been practicing in full-team drills this spring as they recover from offseason surgeries, giving Darby and fellow young cornerbacks Ross Cockrell and Ron Brooks a chance for first-team reps. That figures to change in training camp, pushing Darby down the depth chart. Still, as a second-round pick, Darby has the talent to give McKelvin a run for his starting job this summer.