However, the manager is hopeful he will have the midfield man back fighting fit for the Dark Blues visit to McDiarmid Park this weekend.
Thomson, signed on a free transfer from relegated Hibs this summer, has been out of action since the second week of the new SPFL campaign.
The 29-year-old has not kicked a ball since being forced off after just eight minutes of his side’s 0-0 draw at Inverness back on August 13.
Hartley had expected to have his influential captain back for the League Cup win over Raith last month but he decided to take no risks with Thomson’s calf problem.
Instead, the Scotland international has used the two-week break to complete his rehab and rid himself of the knock.
http://www.eveningtelegraph.co.uk/sport/dundee-fc/dundee-boss-hartley-sweats-over-thomson-s-fitness-1.568407