The 9yr-old pacer faltered near the 800m of Sunday's Hannon Memorial at Oamaru but showed tenacious fighting spirit to regain his gait and finish the race.
He left the track in pain, and early indications were he had fractured the pedal bone in his right foreleg.
However, his trainer-driver Hamish Hunter said initial tests had failed to narrow down the exact problem.
``At the moment, we've had one lot of X-rays and no doubt in a few days' time, we'll have another lot,'' he said.
``Nothing has been pinpointed exactly yet, so that's about where we are.''
Otago Equine Hospital veterinarian Peter Gillespie took good care of the two-time
Hannon Memorial winner after the race, and Hunter said the trip back to Ryal Bush went without incident.
``He was well sedated and well bandaged up for the trip,'' he said.
``Peter Gillespie did his handiwork on him and it was a successful trip.''
Hunter said the entire would be ``quarantined for some time, by the looks of him'' and he hoped the next round of scans would shed some light on the injury and Franco Ledger's immediate future.
``It's not conclusive exactly what the problem is, but the symptoms are that there is certainly an issue there.''
Owned by Hunter and the What Ever Syndicate, Franco Ledger has developed a reputation as a lethal sit-sprinter, winning 25 of his 98 starts for combined earnings of $682,514 across New Zealand and Australia.
Along with his two Hannon Memorial wins in 2012 and 2013, Franco Ledger also won the 2012 Central Otago Trotting Cup, the 2012 Maurice Holmes Vase, the 2013 Invercargill Cup and 2014 Methven Cup.
He joined the Victorian stable of Geoff Webster after the 2014 New Zealand Cup Week, earning a well-deserved group 1 victory in the 2015 Bohemia Crystal at Menangle over 2400m.
While his sprint came to the fore in many of his wins, his most impressive last 400m was possibly in defeat at the 2013 5yr-old emerald division of the Harness Jewels. Chasing down three-time New Zealand Cup winner Terror To Love over a mile, Franco Ledger was unofficially timed running his last 400m in 24.4sec to finish into second place.
