After four months of investigation by the ESPN Enterprise Unit, Sunday’s Outside the Lines (9:30 a.m. ET, ESPN; noon ET ESPNEWS) will show how a suspicious betting pattern on an August 2007 match in an obscure Sopot, Poland tournament prompted the ATP to launch an investigation amid pervasive reports of widespread gambling in the sport.

The British gambling website Betfair, which handled more than $7 million in wagers on the match between No. 4 Nikolay Davydenko of Russia and No. 87 Martin Vassallo Arguello of Argentina, noticed that despite easily winning the first set against his little-known opponent, Davydenko became a bigger and bigger underdog. When Davydenko retired early in the third set after receiving treatment for his foot, Betfair took the unprecedented step of voiding all bets and contacted the ATP.

In addition to extensive interviews, ESPN has obtained never-before-released details of the wagering on the match, which, until now, were known only to those close to the ATP investigation.

Correspondent John Barr details how the suspect betting unfolded and interviews an accomplished gambler who says he bet on the match and is certain that the fix was in that day in Poland

ESPN The Magazine senior writer Shaun Assael obtained a never-before-published internal ATP email that details the suspicious betting activities of Martin Fuhrer, a gambler accused of knowing the outcome of some matches in advance. Assael traveled to Vienna to interview Fuhrer, who acknowledged having friendly associations with some of the players on whom he has won money. In 2003, Fuhrer had a 100-percent win record on Irakli Labadze of Georgia to lose with one betting website, documents say. In one of those matches, Labadze was fined $7,500 for showing "a lack of effort."