Cerra hobbled off during the third quarter in the one-point win over Melbourne at the MCG on Thursday night.
It was the 24-year-old's second game back from a three-week spell on the sidelines with a previous hamstring injury.
Cerra will be sorely missed in Friday's bumper round-10 clash with leaders Sydney at the SCG.
The Blues said Cottrell had a "navicular stress reaction" in his left foot and would be reassessed after their round-14 bye, meaning he will miss at least a month.
Zac Williams (glute) and Marc Pittonet (finger) will have to prove their fitness, while David Cuningham suffered a calf injury in the VFL.
But there could be some relief with hamstrung pair Adam Saad and Jesse Motlop listed as a week away from returning.
GWS will be without influential midfielder Josh Kelly and defender Lachie Ash for the next six weeks.
After reporting calf soreness on Monday following GWS' 20-point loss to Essendon, subsequent scans revealed both players had suffered tendon injuries.
Essendon ruckman Sam Draper will miss six-to-eight weeks after undergoing a knee arthroscopy on Tuesday.
Recruit Xavier Duursma will miss four-to-six weeks with a quad injury but gun defender Jordan Ridley could return from his own quad strain against North Melbourne on Sunday.
Draper, 25, had missed the Bombers' past two games after experiencing pain in his knee when kicking.
The Bombers will be patient with Draper, who had an interrupted pre-season after surgery on a groin injury that derailed the back half of his 2023 season.
Veteran Todd Goldstein has been leading Essendon's ruck department, with support from key forward Peter Wright.
Christian Salem (hamstring) could return for Melbourne against West Coast, but Jacob van Rooyen (concussion) will miss the clash and swingman Daniel Turner (calf) is sidelined for three-to-four weeks.
Richmond young gun Maurice Rioli will miss eight-to-10 weeks after undergoing surgery on a syndesmosis injury, as the Tigers' horror injury list continues to grow.
Jack Graham (hamstring) and Seth Campbell (knee bone bruising) will miss the next one-to-two weeks while Sam Banks (concussion) cannot play this week.
Liam Baker (corked leg) and Dylan Grimes (back) will have to prove their fitness to face Brisbane at the Gabba.
Hawthorn skipper James Sicily (shoulder/ankle) and forward Mabior Chol (wrist) just need to pass fitness tests to return to play against Port Adelaide.
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