The Zimbabwean, who played 24 league matches in his first season for Arrows last term, was scheduled for surgery on Tuesday.
"Yes, he has suffered an Achilles tendon [injury]. It happened at training. He was just about to run and take off and he pulled his Achilles tendon," Arrows coach Clinton Larsen tells KickOff.com.
"These things happen. It's part of the game. Normally it could be six to eight months [out]. It just depends on the player, depends on the recovery, depends on how the operation is done.
"So we'll just wait and see in the second half of the season whether he'll be back or not."
Phiri was sent off in the club's MTN8 opener against Bidvest Wits this season and was suspended for their next two matches against Ajax Cape Town and Bloemfontein Celtic.
Defender Lehlohonolo Nonyane has also been ruled for another week or two with a hamstring problem sustained in the 1-1 draw with Celtic on August 23. Nonyane missed much of 2016/17 after damaging his groin in October 2016.
"Nonyane will be back in the next week to two weeks, so he's also out," adds Larsen.
However, right-back Siyabonga Dube is back for tonight's league clash with Wits at Bidvest Stadium (19h30) after serving a two-game ban.
Dube, who was suspended following his dismissal against the Students in the MTN8, played for Abafana Bes'thende's reserve team in the MultiChoice Diski Challenge on the weekend.
The 21-year-old was a contender for the Nedbank Cup Young Player of the Tournament award last season, losing out to teammate Nduduzo Sibiya.