Sumlin said on ESPN Radio's "SVP & Russillo" that he has not yet talked to the Heisman-winning quarterback about his decision, but he outlined a timeline for Manziel's announcement.
"We haven't had that conversation," Sumlin said. "My job is to get him all the facts that we can get him. We'll have that discussion after the Missouri game, certainly during the bowl preparation. I'm sure the announcement will be made at that time."
Texas A&M concludes its regular season Nov. 30 at Missouri, and the earliest bowl affiliated with the SEC is Dec. 30.
2014 is the first year that Manziel, a redshirt sophomore, is eligible to enter the NFL draft. Manziel is the 13th overall player and third quarterback on Mel Kiper Jr.'s Big Board projections.
Manziel, who has thrown 31 touchdown passes and run for eight more this season, is a top candidate to win the Heisman for the second straight year.
Sumlin said he's happy with how Manziel has dealt with the pressure and national attention.
"He's handled things on the field as well as any player in the country," Sumlin said. "His numbers are better than they were last year. And I've had a number of people tell me there's no more exciting college football player in the country than he is, and he's the guy they like to watch.
"He's a special talent. His energy, his leadership on the team is evident, and he continues to get better every week."