Chorus says it connected a record number of homes to UFB fibre during June as the Rugby World Cup approached.
But even if it can keep up the record pace, hundreds of thousands of homes will still miss out.
The network company says it received 33,000 fibre connection orders during July and completed about 26,000 connections.
That was well up on the 27,000 orders and 22,000 fibre installations and connections completed in June.
A spokesman tells the Herald that Chorus can connect another 21,000 homes between now and the RWC opener on September 20.
But that will still leave around 600,000 homes that have fibre down their street, but have yet to be connected by Chorus.
Chorus is on track with its nationwide rollout, which it is due to complete by 2022. The problem is that its timetable does not coincide with Spark Sport's.
Earlier, the smaller Enable Networks said around 100,000 of the 200,000 homes it has rolled UFB fibre past in Canterbury had connected. As of the first week of June, it had the capacity to connect another 10,000 by RWC kick-off.
Experts say UFB (ultrafast broadband) fibre is the best type of internet connection for watching streaming video - such as Spark Sport's looming Rugby World Cup coverage - particularly if you want to cast it to a big screen TV, or other people in your household want to use the internet at the same time.
Spark Sport says it's confident that the Rugby World Cup can be successfully streamed into urban homes. Its app will automatically adjust in quality to accommodate a slow or overloaded line.
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In rural areas, the situation is trickier. MPs were told earlier this year that upward of 40,000 rural homes don't have good enough broadband to watch the Rugby World Cup via broadband.
Spark's safety net measures include offering the RWC through 150 rural schools (which all have fibre connections, and can potentially offer community viewing after hours); making Spark Sport available to pubs and clubs at a household rather than commercial rate, making 12 games available through TVNZ.
The games on TVNZ will include all of the All Blacks' pool games on a one-hour delay, the AB's assumed quarter-final on a one-hour delay and the semis and the final live.