By ESPNSTAR.com staff
The midfielder picked up the injury during Barca's 3-2 win at Sevilla on Saturday and was not in the squad for the club's midweek UEFA Champions League encounter with Benfica.
Following a scan, the club confirmed on its website that the Thiago will be sidelined for at least eight weeks.
A statement read: "Thiago will be out for eight weeks after tests today [Sunday] confirmed damaged ligament in his right knee."
"The player will undergo conservative treatment with doctors estimating he'll be out for up to eight weeks."
It is expected that he will miss a total of eleven games - against Benfica, Madrid, Deportivo, Celtic and Rayo in October and Celta, Celtic, Mallorca, Zaragoza, Spartak and Levante in November.
There is some good news though as Barca midfielder Andres Iniesta is poised to return from a four-match lay-off for Tuesday's Group G match in Lisbon after recovering from a muscle injury suffered on international duty with Spain.