He has made sure his teammates cherish Georgia's first appearance in the tournament since 2011.
''I've told guys about this experience,'' Thornton said. ''It's such a unique and great experience. I was telling the guys it's my favorite memory.''
Another senior, Nemanja Djurisic, said Thornton's words made an impact.
''He's the only guy,'' Djurisic said. ''You can see through his determination and his will and his leadership that he knew how good it is and how special the moment is. He was eager to help us through good and bad to get us in there.''
The return to the tournament is a reward for Thornton's difficult career. He overcame two knee surgeries, including one which led to a medical redshirt in the 2012-13 season.
Thornton was a backup when Georgia lost to Washington in the NCAA's first round four years ago. He says the long-awaited return has given him an opportunity to reflect on his career.
''There have been some things that have happened that really make me thankful to have this moment and this opportunity,'' he said. ''I've shared that a little bit. We have a chance not just to be in the NCAA Tournament but to have success in the tournament.''
Thornton led Georgia (21-11) with his career-best averages of 12.3 points and 7.2 rebounds. Southeastern Conference coaches named the senior to their all-defensive team, and he was an honorable mention selection to the All-SEC team this week.
Thornton's value to the team became clear when he missed two games with a concussion this season. Georgia lost both games.
With the exception of former walk-on Taylor Echols, Thornton and Djurisic are Georgia's only seniors. Coach Mark Fox said they rank among the best leaders he has coached.
''It means a great deal to me,'' Fox said. ''Those two guys have been phenomenal seniors for us. ... There's been no better leadership in the time I've been here than what Neme and Marcus have given us.''
Georgia's NCAA hopes took a hit following back-to-back home losses to Auburn and South Carolina in mid-February. The seniors led the way as the Bulldogs responded by winning four of their last five regular-season games.
Thornton had 18 points and 13 rebounds in an important 76-72 win at Mississippi on Feb. 25. He had 15 points and eight rebounds in a 74-62 SEC Tournament win over South Carolina which helped to solidify the Bulldogs' No. 10 seed in the NCAA field.
Junior Kenny Gaines said he wanted to make sure Thornton had one more trip to the NCAA Tournament.
''To do it for this group of guys like Marcus, who has been through so much, means a lot,'' Gaines said. ''He battled back and is undoubtedly our leader as a senior. We're just so excited and elated to get him in there. That means more than anything.''