by John Shinal, Special for USA TODAY (includes quote by Brian Solis)

The second-quarter surge in digital advertising revenue just reported by Google, along with the large quarterly gain also expected from Facebook, shows just how much of Twitter’s market opportunity is being captured by its competitors.

The huge gains in sales and profit at its much-larger rivals come as Twitter on Tuesday is expected to report yet another quarterly operating loss for the same period amid disappointing user growth. In mid-morning trading, Twitter shares are down 3.5%, to $34.12, and is near a 52-week low.

The San Francisco-based social media company is expected to post operating and net losses of more than $500 million in 2015, according to Wall Street estimates despite its own surging sales.

That figure is on top of the $1.55 billion in aggregate operating losses Twitter incurred during the five years ended in 2014.

After almost a decade, “Twitter is still trying to figure out its business,” said Brian Solis, an analyst with the San Francisco-based industry research firm Altimeter Group.