Walker, who was selected by the Bucs in the third round of last April's draft, injured his left thumb during last Friday's practice.
"Upon our return we did extensive x-rays and found that he's going to be out for the year," said Gruden. "We hate to see that."
Walker was inactive for Tampa Bay's first four regular season games, which might make his prognosis a little easier to swallow. The team is expected to place Walker on the injured reserve, which will open a spot on Tampa Bay's 53-man roster.
In other injury news, Bucs long snapper Mike Solwold suffered a left foot sprain against the Bengals on Sunday and will be listed as out for Tampa Bay's game at Atlanta.
The extent of Solwold's injury will be determined later Monday, but the Buccaneers will begin searching the free agent market for a temporary replacement. Tampa Bay could also possibly use tight end Ken Dilger or guard Russ Hochstein as a temporary replacement since they both have experience at the long snapper position.
Gruden said Monday that right tackle Kenyatta Walker, who was expected to miss at least one month with the high ankle sprain he suffered in Tampa Bay's game against St. Louis, had showed some improvement, but he will be listed as doubtful for Sunday's game at Atlanta.
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