Maybe this explains the timing, since after his injury he probably dropped all appeals so it could start ASAP:
"Players who test positive for either their first or second tests are given the option to appeal, in which scientific tests will be conducted to prove validity of test. Within that period of time, they are restricted from participation in all baseball activity. If an appeal is granted, the suspension may be reduced by 40 games for the first offense or 80 games for the second offense. There is no appeal for a third offense. All suspensions are without pay. In addition, a suspended player can be replaced on the active roster by another player.
If a player is on the disabled list, the suspension is served while on the disabled list. Unless a suspension is reduced on appeal, a suspended player is not allowed to participate in that year's post-season even if his suspension ends before then.
Players who receive a lifetime ban after a third positive test may apply for reinstatement after one year and be eligible to be reinstated after two years."
https://en.wikipedia.org/wiki/Major_League_Baseball_drug_policy