Cromartie's decision not to re-sign with the Cardinals after one season kicked off an offseason battle between Cardinals cornerbacks Jerraud Powers and Justin Bethel. Powers started all 16 games at outside corner in 2013 and moved inside to nickel corner last season. Bethel played 93 defensive snaps in 2014, according to ESPN Stats & Information.
Adding Dennard will give the Cardinals depth with versatile corners, general manager Steve Keim said Wednesday on SiriusXM NFL Radio. Keim said Dennard can play inside, outside and nickel corner and is "quick footed" and tough.
Dennard will be the 11th cornerback on the roster heading into organized team activities May 19.
The 25-year-old was a 2012 seventh-round pick who had been a starter at times for the Patriots. He appeared in 29 regular-season games over the past three seasons, producing five interceptions and 90 tackles. He also played four playoff games and added two more interceptions.
In 2014, Dennard slid down the depth chart before being placed on season-ending injured reserve in December before New England's regular-season finale.
Dennard served 35 of a possible 60 days in a Nebraska detention center last year following a probation violation.
He was arrested in July 2013 for driving under the influence, which violated his previous probation, stemming from a 2012 conviction of felony assault of a police officer in an incident outside a Lincoln, Nebraska, bar just days before the 2012 NFL draft.
Dennard's original arrest affected his draft status, as he slid into the seventh round after being projected by many experts to land in the top two rounds.
ESPN NFL Insider Field Yates, Cardinals reporter Josh Weinfuss and Patriots reporter Mike Reiss contributed to this report.