Watch: Rihanna Performs at 2011 Jingle Bell Ball

Reports that Rihanna may be suffering from exhaustion have just received new fuel: she was one of the performers at the Capital FM's 2011 Jingle Bell Ball at London's O2 Arena and, to be frank, her number was far below standards.

Fans must know only too well that, while she's not one of the strongest vocalists out there, Rihanna rarely disappoints, having been born an excellent performer.

That wasn't so apparent over the weekend, when she seemed to be out of breath, exhausted and, yes, somewhat bored for most of the routine.

Rihanna's set included “We Found Love,” “Only Girl (In the World),” “What's My Name,” “Umbrella” and “S&M,” as the videos below will confirm.

While the first two songs were delivered in an excellent manner, during the last 3, one distinctly gets the impression that Rihanna is about to throw down the mic and just walk out – or simply stop singing altogether.

Her voice cracks, she's out of breath and she simply doesn't have the energy to do this anymore. As reports online have it, she's in need of a break – badly.

Check out Rihanna's performance and then drop us a line with your thoughts: does she sound out of it or is it just an impression?

Rihanna, “Only Girl (In the World)”



Rihanna, “What's My Name”



Rihanna, “Umbrella”



Rihanna, “S&M”