The Saints have hired Rob Ryan as defensive coordinator, hoping they can overhaul a unit that was historically bad last season. Ryan, the brother of Jets coach Rex Ryan, spent the past two seasons as Dallas’s defensive coordinator. He was fired after last season, when his defense ranked 19th. Last year, New Orleans allowed 7,042 yards under defensive coordinator Steve Spagnuolo, the worst total for a season in NFL history. Saints coach Sean Payton said he also added Stan Kwan as an assistant special teams coach. Kwan was a special teams assistant in Buffalo the past three seasons . . . Receiver Anquan Boldin said Friday that he would retire if Baltimore cuts him. The 32-year-old said on NBC Sports Radio that he wants to retire a Raven, but the team may have to make salary-cap related moves in the offseason. Boldin has one year left on his four-year, $25 million deal, and is due $6 million next season . . . Doug Kenna, quarterback of West Point’s 1944 undefeated national championship team, died Jan. 28 in North Palm Beach, Fla., according to a longtime friend. He was 88.