Thiago had been out since the end of April, having undergone hip surgery, before coming off the bench for the final five minutes on Sunday.
It was a significant occasion for the Spaniard, despite the 3-1 loss, and came exactly a year to the day since his last start for the club.
Unfortunately, it came at a cost, with Thiago now injured again.
According to the Times‘ Paul Joyce, the 32-year-old has suffered an unspecified muscle issue and now faces more time out of the picture.
But it is not likely to be positive news for the midfielder, who had already experienced a series of setbacks in his recovery.
Thiago had initially returned to first-team training in August, having sat out pre-season, before being sidelined again as the club took every caution with his recovery.
He was rarely involved again in full sessions between then and the end of January, before taking his place alongside team-mates at the AXA Training Centre again pre-Chelsea.
Thiago‘s contract expires at the end of the season, with no talks over an extension planned.