The South Australian Cricket Association (SACA) said Lehmann's condition was picked up during a routine check-up as follow up to his surgery to repair a damaged Achilles tendon.
SACA physiotherapist John Porter said Lehmann's condition would be monitored this week.
''It has been identified early and Darren will undergo blood-thinning treatment for the next three months,'' Porter said.
''We are very confident that this will not delay his recovery from the Achilles operation and that he will be fit to play with the Redbacks when the season starts in October.'' Lehmann stood down as South Australian captain at the end of last season but remains a contracted player and is expected to continue to play as a batsman at state level.