He is now a free agent and is drawing consideration from the New York Jets, ESPNNewYork.com has learned.
Thomas was the highest-priced free-agent acquisition in team history, signing a five-year, $35 million contract in 2007, but he turned out to be one of the biggest personnel missteps in Bill Belichick's 11-year tenure.
In the end, it was a pairing in which both sides didn't get what they felt was advertised.
Thomas had issues with his role, expecting to be used as more of a pure pass-rusher, while the Patriots were disappointed with Thomas' production and presence in the locker room.
The 32-year-old Thomas wasn't expected back with the Patriots in 2010. The main question was whether he would be released or traded, and his $4.9 million base salary for 2010 made a trade unlikely.
Given the timing of the release, it appears the Patriots tried to trade Thomas during the draft and when nothing materialized, they went ahead with the release.
"After the draft, we talked about the personnel and looked at our roster and so forth, and we made that decision to move on with the players that we have," Belichick told Boston sports radio station WEEI on Monday afternoon. "He was a good football player, he came in and had a heck of a year for us in '07. Again, at this point in time, we felt like this was the direction we had to go on."
Thomas' final season in New England was a rocky one, highlighted by his benching for a game against the Tennessee Titans on Oct. 18, and then being sent home with three other players for being late to an 8 a.m. meeting on a snowy, icy December morning. That contrasted the early days of Thomas' tenure, when he printed "Humble Pie" T-shirts and distributed them to teammates as a sign of how he was buying in to the Patriots' approach.
The 32-year-old Thomas played in 39 regular-season games for the Patriots, with 35 starts, totaling 148 tackles and 14.5 sacks. Thomas thrived under Jets head coach Rex Ryan when Ryan was the Baltimore Ravens' defensive coordinator and Thomas was his star linebacker.
Thomas played under Ryan from 2001 to 2006 in Baltimore. Under Ryan's guidance, he made two Pro Bowls for the Ravens before bolting to New England.
The widespread belief is that Thomas will join his old coach, but the Jets still are assessing the situation. The recent addition of former Dolphins pass rusher Jason Taylor gives them three veteran outside linebackers (Calvin Pace and Bryan Thomas are the others), but Thomas is more than just an outside linebacker.
Ryan loves his versatility. Thomas, 6-foot-2, 270 pounds, can play inside linebacker, defensive end and slide inside to defensive tackle in certain packages. His familiarity with Ryan's system is another attractive attribute; it would be a seamless transition.
Jets linebacker Bart Scott said on "Mike & Mike in the Morning" on ESPN Radio in March that Thomas would like to play for the Jets if he were released by New England.
"It's funny," Scott said. "I was hanging with Adalius Thomas for Super Bowl weekend. We're buddies from back in the day. He made it public that he's expressed an interest in joining Rex. I think some of his better years of his career have been a part of the Ravens' defense and under Rex Ryan's tutelage. It'll be exciting."
Thomas later told the Boston Herald that conversation never happened and that he had never discussed joining the Jets with Scott.
"I've heard of all the chatter up there about me," Thomas wrote the Herald. "It was about something Bart Scott said on TV, [and] that's not what was said. I have never told anyone that I wanted to leave and go play for the Jets."
Thomas told Boston radio station 98.5 The Sports Hub in February that he wasn't sure whether he would be released but said he wanted to play "somewhere where I'm wanted and where I'm going to have fun. That's where I want to be."
He stopped short of saying he felt unwanted in New England, but told 98.5: "I definitely didn't have fun. It was definitely a frustrating year as far as that goes."
Information from ESPNBoston.com's Mike Reiss and ESPNNewYork.com's Rich Cimini was used in this report.