Grubb was tabbed to lead the Washington offense in 2022 and had significant success. The Huskies finished No. 1 in third down conversion percentage and passing offense. No. 2 in total offense and No. 5 in total first downs.
O'Brien has extensive experience working with Belichick as the pair worked together from 2007-11. He's worked with receivers and quarterbacks in the pros and spent time as offensive coordinator under Belichick, while together the pair won four division championships and two AFC Championships.
The Patriots offense finished 26th in the league in yards per game and 17th in points per game with co-offensive coordinators Matt Patricia and Joe Judge. Hiring O'Brien to fix the offense gives Belichick a trusted mind that can get the most out of third-year quarterback Mac Jones.
Though you never want to put too much blame on one person, it's hard not to look at the last two seasons for the Alabama Crimson Tide and wonder what might've been had Bill O'Brien not been the offensive coordinator.