The 33-year-old was forced off with just 36 minutes of the game gone, having first felt the issue some 14 minutes earlier.
That the Barca captain carried on can either be interpreted as good or bad news, with the problem seemingly not serious enough to warrant an immediate substitution, though there is the fear that he may have further damaged the muscle by playing on.
So far, Barca have refused to set a date for his return and will not do so until the midfield metronome has undergone tests on the problem.
However, with the game against Chelsea at the Camp Nou just 10 days away, the club legend must be considered a major doubt.
Iniesta's potential absence is exacerbated further by the fact that Philippe Coutinho is ineligible for the Champions League, having featured for Liverpool earlier in the competition.
4 March 2018