Rihanna and Chris Brown's relationship under strain due to busy work schedules

The pair spent the weekend apart and 23-year-old Brown was spotted flirting with a mystery blonde in Hollywood club Playhouse on Saturday, while his girlfriend was away on tour.

Rihanna, on the other hand, responded by attending an LA Lakers basketball game with a male friend on Sunday, just days after Brown admitted he finds it hard not to be the jealous boyfriend.

However, friends insist that despite their busy schedules they are still going strong.

A friend of the couple told celebrity website HollywoodLife.com: Theyre cool and when something changes between them, thats between them. They both have a lot going on in their careers right now and [theyre] focused on their work.

Theyve been trying to connect but it hasnt been clicking for them. It aint like Rihannas got time to just chill and run, though shes on tour and her schedule is way too tight.

Brown is still on probation for brutally assaulting his 25-year-old Barbadian girlfriend before the Grammys in February 2009.