In a media briefing issued after fulltime of the first of three huge games tonight - the Wallabies versus Fiji - Spark said about 44,000 subscribers were online for kickoff in the clash; which was won 39-21 by the Wallabies after an early scare from Fiji.
But by fulltime the number of individual streamers had almost reached 88,000.
"Tonight's numbers so far are significantly more than last night's tournament opening match between Japan and Russia," a statement said. "Throughout the game, the Spark Sport streaming service worked well from a platform and broadband network perspective.
"As we always knew, today would be a very busy day for Spark Sport. We've substantially increased our Spark Sport care teams to help our customers with their in-home set up and streaming experience.
"So far today, we've supported approximately 10,000 customers through phone calls, online chat and Facebook and Twitter interactions to get their Spark Sport working as best as possible, based on their in-home set up and devices."
Spark Sport said it had also seen a strong increase in sales and voucher redemptions of its Rugby World Cup Tournament Pass over the past 48 hours.
It was expecting "more viewers" for the second clash of the night, France versus Argentina, and then tonight's big Pool B clash; the All Blacks versus Springboks showdown.
On opening night of the tournament on Friday, within a few minutes of the official opening ceremony dozens of rugby fans took to social media to express their frustrations with complaints ranging from freezing to lagging and glitching.
Spark responded saying the platform was performing "extremely well" and the issues experienced were limited to a "tiny fraction" of customers.
"There are no systemic issues with the platform and we're delighted with how the network is performing," Andrew Pirie, Spark's corporate relations lead, told the Herald.
"We've had literally a few dozen individual customers with device concerns and glitches and we have been helping them through it."
The complaints received by Spark came just hours after some customers received a bombshell letter – on the day of the World Cup opening game – informing them that the broadband at their addresses weren't up to snuff, despite being sold a World Cup Tournament Pass with the deal they initially signed up to.
