DeBoer was a little more tempered after Thornton skated on a line with Joe Pavelski and Evander Kane during practice Tuesday.
"He's never going to put himself out [of the lineup]," DeBoer said. "The reality of this is the antibiotics have to do their job. We can't risk a second infection. I would put it as doubtful. I would never count against him, but the bottom line is we have to let the antibiotics do their job, and their job. That doesn't happen overnight."
DeBoer was noncommittal when asked if Thornton could play Saturday, when San Jose hosts the New York Islanders.
"Well, I don't know," DeBoer said. "I'm not as versed in how long that takes. When he says you're waiting on blood tests, I think those are the markers for is the infection gone or isn't it gone. So I don't know if there's a timeframe on that until we get that back."
Thornton said he understands the risks of coming back too quickly.
"[The Sharks] want to make sure, get rid of it now so I don't have to deal with it in December, January, February," he said. "Just squash it now, get me healthy then I'll be ready to go."
Thornton had surgery to repair torn ligaments in each knee within the past year and a half.
He tore the MCL and ACL in his left knee on April 2, 2017. He returned two weeks later and played the final four games of a six-game loss to the Edmonton Oilers in the Western Conference First Round before having surgery April 24, 2017.
Last season, he had 36 points (13 goals, 23 assists) in 47 games before he tore the MCL and ACL in his right knee Jan. 23 and had surgery two days later.
Thornton has one assist in two games this season. He ranks 12th in NHL history with 1,031 assists and 16th with 1,428 points.
The Sharks recalled center Dylan Gambrell from the San Jose Barracuda of the American Hockey League on Tuesday. Gambrell, a second-round pick (No. 60) in the 2016 NHL Draft, had no points in three games with San Jose last season.
NHL correspondent Eric Gilmore contributed to this report
