The Bayern Munich coach has confirmed the midfielder's injury he suffered against Nurnberg on Saturday is worse than first thought and it could be November before he returns
The 22-year-old summer signing from Barcelona suffered ankle ligament damage during Saturday’s 2-0 victory over Nurnberg, with an initial prognosis suggesting the midfielder could be sidelined for up to seven weeks.
However, Guardiola has confirmed the absence is likely to be much longer, and conceded losing his playmaker would be a "huge blow".
"He will be out of action for more than two months - possibly until halfway through November," Guardiola told Bild.
"He played on for more than 20 minutes after picking up the injury, which shows that he has a lot of character."
The Spain international was withdrawn just after the hour mark of Saturday’s Bavarian derby at the Allianz Arena, with scans showing damage to his ankle ligaments.
The loss of Thiago gives boss Guardiola further selection headaches, with a high proportion of his ample central midfield stock short of full fitness.
Javi Martinez and Mario Gotze’s appearances have been restricted so far this season, yet it appears Thiago’s lack of availability will prove most problematic to Guardiola.
He added: "This is a huge blow and we will really miss him. He has certain abilities that others don't possess. We will have to find other solutions."
Bayern face a visit to Freiburg in the Bundesliga on Tuesday, before meeting Chelsea in Friday’s Uefa Super Cup final in Prague.