The New Zealand international striker is out with a groin injury to leave manager Peter Reid desperately short of attacking options.
Reid said: "We rested him for two weeks but he has soreness in the groin. It's too sore to carry on."
Reid will choose a replacement from Joe Mason, Rory Patterson and winger Yannick Bolasie, who has played as a forward earlier in Argyle's campaign.
There could even be a first call-up to a matchday squad for 19-year-old striker Liam Head while captain Carl Fletcher is also doubtful to face the Saddlers because of a foot injury.
Versatile midfielder Chris Clark remains sidelined by the medial knee ligament injury he suffered in a defeat to Rochdale in March. Midfielder Kari Arnason returns from a two-match suspension activated after picking up his 10th yellow card of the season.
Source: PA
Source: PA