The Buffalo Bills have welcomed plenty of new pieces into the fold this offseason, particularly on the defensive side of the ball.As part of an overhaul led by new defensive coordinator Jim Leonhard, the Bills remade their edge rusher room, signed two safeties with starting experience and drafted potential starters at cornerback and linebacker.While multiple core pieces return, everyone must establish themselves in a new system in front of new coaches. That task is especially important for any newcomers who have aspirations to start.Sports Illustrated senior reporter Albert Breer mentioned four defensive newcomers who will be tested during training camp."Speaking of new coaches, the Bills’s shift in philosophy comes on the head-coaching side, since new boss Joe Brady was promoted from the offensive coordinator spot. So veteran additions such as Bradley Chubb, C.J. Gardner-Johnson and Geno Stone, and draft picks like DE T.J. Parker are headed into a critical summer," said Breer.Wisconsin head coach Jim Leonhard is shown during the second quarter of their game against Maryland Saturday, Nov. 5, 2022, at Camp Randall Stadium in Madison | USA TODAY Network via Reuters ConnectConversely, Breer suggested that wide receiver DJ Moore's familiarity with head coach Joe Brady will make matters less challenging for him this summer.As for what's at stake and how they will fare, here's are some thoughts on the four potential defensive starters.OLB Bradley ChubbChubb is changing teams, but he's joining a familiar scheme that could potentially bring out the best in him."He's played in very similar defenses the majority of his career, even at Miami, so excited to have him for the player that he is - the experience, the versatility he has, and the leadership," said Leonhard.In a positive development for the Bills, the former No. 5 overall draft pick has already started establishing himself as a leader. In that spirit, Chubb invited Parker to train with him in South Florida during the current break.Although Chubb, whose 8.5 sacks were enough to lead the Bills in 2025, is the presumed starter opposite Greg Rousseau, he must work to leave no doubt this summer. Buffalo needs him to become the closer that the pass rush has lacked for years.Miami Dolphins linebacker Bradley Chubb, top, and defensive tackle Christian Wilkins, bottom, hit New York Jets quarterback Zach Wilson (2) causing a fumble during the first half of an NFL game at Hard Rock Stadium in Miami Gardens, Dec. 17, 2023. | USA TODAY Network via Reuters ConnectS Chauncey Gardner-JohnsonGardner-Johnson's explosive personality has resulted in the talented defensive back playing for four different teams in the past three seasons. Although it's still early, the fiery safety has seemingly struck all the right chords thus far."We're excited about just his passion and energy for the game and what he brings into the building every day," said Leonhard.We wrote about the Super Bowl LIX champion making his presence felt during June minicamp when he managed to pick off a pass from Josh Allen."He's a competitor. He's the loudest guy in the room at all times. He's a constant competitor, and nothing that he does is half speed. He does it full speed," said Allen.Gardner-Johnson, who notched two six-interception seasons for the Philadelphia Eagles (2022, 2024), is the favorite to start at safety alongside 2024 second-round pick Cole Bishop.Oct 9, 2022; Glendale, Arizona, U.S.; Philadelphia Eagles safety C.J. Gardner-Johnson (23) intercepts a pass by Arizona Cardinals quarterback Kyler Murray during the first quarter at State Farm Stadium. | USA TODAY Network via Reuters ConnectS Geno StoneStone has seemingly flown under the radar a bit since signing with the Bills in mid-March. The 27-year-old, who has not missed a game in the last four seasons, figures to compete against the Gardner-Johnson for a starting role."They're gonna get a guy that's gonna compete everyday, a guy that's gonna be in the right spots at the right time, and a leader. Now, I'm seven years in the league. I feel like I've been around a lot to know what it takes to be a pro in this league and what it takes to win," said Stone back in March.Stone, who decided to sign with the Bills on the recommendation by fellow Iowa alumnus Micah Hyde, has made 36 consecutive starts and likely intends to extend that streak with the Bills. We recently named the safety, who had seven interceptions for the Baltimore Ravens in 2023, as one of three most under-appreciated offseason additions.With veteran Damar Hamlin also in the mix, Stone will face plenty of competition this summer.Baltimore Ravens safety Geno Stone (26) intercepts a pass intended for Cincinnati Bengals wide receiver Tee Higgins (5) in the third quarter of a Week 2 NFL football game between the Baltimore Ravens and the Cincinnati Bengals Sunday, Sept. 17, 2023, at Paycor Stadium in Cincinnati. | USA TODAY Network via Reuters ConnectOLB TJ Parker (R)A rookie's first summer is always an important one, especially if the player is expecting to hold a meaningful role in the months ahead.If he plans to break into the edge rusher rotation, it's imperative that Parker is available to learn on the field during training camp and become acclimated to the speed of the pro game. Ideally, the Clemson product can rediscover his 2024 form when he totaled 11.0 sacks.Bills' veteran Ed Oliver called Parker a "cheat code" during June minicamp, and the rookie looks like he belongs although the pads have to come on."We’re really excited to get him," said Leonhard. "We had our eyes on him early in the [draft] process, and just excited to see his mentality, his work ethic, and just the buy-in with the program."With Greg Rousseau and Chubb the probable starters, and Michael Hoecht likely to see ample time, Parker projects as the Bills' fourth edge rusher heading into training camp.Feb 26, 2026; Indianapolis, IN, USA; Clemson defensive lineman TJ Parker (DL55) during the NFL Scouting Combine at Lucas Oil Stadium. | IMAGN IMAGES via Reuters Connect— Sign up for OnSI’s Free Buffalo Bills Newsletter —Add us as a preferred source on GoogleFollow