Rizwan and Irfan both suffered hamstring injuries in the third match in Rawalpindi
CAS said it had reached its decision "in view of some mitigating factors" although it added that "the athlete has failed to establish that she bears no significant fault or negligence."
Blake tested positive for the banned stimulant methylhexanamine at the 2012 Olympic trials, her second doping offence after she tested positive for ephedrine in 2006 for which she was banned for nine months.
Blake finished sixth at the trials and was picked as a relay runner for the London Olympics but did not compete at the Games.