After leaving Bedford School, where he had played cricket for the school alongside Alastair Cook, following his A Levels in 2000, Shankar proceeded to read law at Cambridge University. It was for the university cricket club that he made his first-class debut against Middlesex in 2002. Shankar played first-class cricket for the university from 2002 to 2005, playing his final first-class match against Oxford University, while on occasion he captained the university. Shankar played 12 first-class matches for the University, scoring 384 runs at an average of 27.42. His one innings of note came against Oxford University in 2002, when he scored 143 runs from 297 balls, before being dismissed by Stephen Hawinkels. This was Shankar's only first-class century and was the only time he passed fifty. The bowling in the match was later described by Cambridge University coach Chris Scott as "unbelievably bad".
Shankar made his debut for Bedfordshire while still at Bedford School, making his debut against Norfolk in the 2000 Minor Counties Championship. Between 2000 and 2006, Shankar played infrequently for Bedfordshire, making 21 Minor Counties Championship appearances and 2 MCCA Knockout Trophy appearances, which came in 2006. It was for Bedfordshire that he made his List A debut for, against Sussex in the 2005 Cheltenham & Gloucester Trophy at Wardown Park. He was dismissed for 27 runs in this match by Jason Lewry, which was the second highest score in Bedfordshires' innings. During this period, he played Second XI cricket for the Middlesex Second XI, Worcestershire Second XI and Sussex Second XI, however his career was interrupted for 18 months when he suffered from glandular fever.
After representing the Lancashire Second XI in 2008, Shankar was given a two-year contract with Lancashire. Lancashire cricket coach, Mike Watkinson, stated "Adrian is a quality young batsman who fills a gap in our player development programme. He has attracted interest from a number of other counties which confirms his potential". While on the Lancashire staff, Shankar chose to study part-time for a two-year masters course in international relations, also at Cambridge. It fitted in with Shankar's ambition to play cricket for Lancashire as the course required that he only had to be in Cambridge for six weeks of the year. However, Shankar failed to impress and did not play for Lancashire's first team.
While playing cricket in Sri Lanka in the "Sri Lankan Mercantile League" (later discovered to be a fictional competition likely invented by Shankar himself) he came to the attention of Worcestershire, and he signed a contract with the injury hit club in May 2011. Shankar was put straight into the Worcestershire first team, making his debut for the county in the Clydesdale Bank 40 against Middlesex, in what would be his only List A appearance for the team. In this match he opened the batting with Moeen Ali, but was dismissed for a duck by Tim Murtagh. He made a single first-class appearance for the county, which came against Durham. He scored 10 unbeaten runs in Worcestershire's first-innings, before retiring hurt with a strained cruciate ligament which was set to rule him out for six weeks.
Two weeks after signing for his new county, his claims that he was three years younger than his actual age and that he had enjoyed a successful season playing high level cricket in Sri Lanka turned out to be false. Shankar was immediately released from his contract. The cricket he played in Sri Lanka was played at a minor level, with scorecards of the series not appearing on respected archiving websites such as CricketArchive and Cricinfo, a fact it appears Worcestershire failed to check. In light of this, the England and Wales Cricket Board asked Bedfordshire, for whom he was still registered to play Minor counties cricket for, to remove him from their list of eligible players. Worcestershire also passed his registration documents to West Mercia Police, who later decided not to pursue criminal charges.
Shankar's deception had begun at Lancashire, with Shankar claiming his age was 23. Upon his signing with the county, Lancashire released a press statement which stated the Cambridge University coach referring to him as one of the finest young players the university side had seen since John Crawley. Chris Scott contacted Lancashire to deny having made such a claim, saying "I phoned Lancashire and made it clear that I'd never said anything of the sort", before going on to say "He was a poor player and there's no way I would have recommended him." In response to the situation, Bedfordshire president Mike Green had to say "Frankly we [Bedfordshire] were amazed when we found out he was signing for Worcestershire because he would have struggled to get into our side. He hadn’t been good enough to get into our first XI for a good six or seven years." Former Lancashire player Luke Sutton, writing in his blog for the Daily Mail remembered Shankar's spell at Lancashire and recounted his and his fellow Lancashire teammates doubts about Shankar's claims. Sutton recalled the first doubt being that Shankar looked out of his depth. His other stories also didn't appear to add up, with Shankar claiming he had been part of the Arsenal Academy, but according to Sutton when they played football in warm ups he wasn't particularly good. Another claim that seeded further doubts was that Shankar had claimed to have played tennis at a national level, but when he played against teammates he was distinctly average. Doubts about his age also circulated at Lancashire, with rumours saying his was 3 years older than he claimed he was. Sutton confronted Shankar on these rumours, and when asked why the rumours existed, Shankar claimed he was on a life support machine for the first three years of his life, saying this made his body physically three years younger than it was. When Sutton questioned the fact he would still continue to grow under these circumstances, he replied "no I didn't" and proceeded to walk off.