Sandeep Patil was born on 8 August 1956 in Bombay. His father, Madhusudan Patil, was a former first class cricketer, national level badminton player and skilled player of tennis and football. He grew up in the Shivaji Park area in Bombay, studied in Balmohan Vidyamandir and Ramnarain Ruia College and was coached by Ankush 'Anna' Vaidya.

In the early part of his career Patil was as much a medium pacer who bowled off the wrong foot, as he was a batsman. Following three successful years for the Bombay university in the Rohinton Baria Trophy, he made the Bombay Ranji team in 1975–76. After being on and off the team for three seasons, he played his first major innings against Delhi in the 1979 semifinal. Going in at No.6 after Bombay lost the first four wickets for 72, Patil hit 145 in 276 minutes with 18 fours and a six, none of his partners made more than 25. Patil played for Edmonton in the Middlesex league in 1979 and 1980, and for Somerset 'B' in the latter year.

Australia and Pakistan visited India in 1979–80. Patil appeared in tour matches for West Zone against both teams, scoring 44 and 23 against Australia, and 68 and 71 against Pakistan. This earned him the selection in the last two Test matches against Pakistan. A week before making the debut, he made his career best first class score against Saurashtra at the Wankhede Stadium. Coming in to bat in the second morning he was 45* at lunch, reached his hundred in 139 balls scoring 105 in the second session, and ended up with 210 made in 205 balls with seven sixes and nineteen fours. The last of the sixes cleared the stadium (a very rare feat at the Wankhede) and landed in the hockey grounds outside. Patil made 62 in the final Test at Calcutta, appeared in the Golden Jubilee Test against England later in the season and was selected for the tour of Australia in 1980–81.

In the early matches of the Australian tour, he scored 116 against South Australia, which included Rodney Hogg, and 60 and 97 against Queensland which had Jeff Thomson, Dennis Lillee, Geoff Dymock and Carl Rackemann. He won the man of the match on his ODI debut for a 64 against Australia.

In the first innings of the first Test at Sydney Patil had reached 65 when just before the tea break on the first day, he was hit on the throat by Hogg. Continuing without a helmet, he was hit over the right ear by a bouncer by Len Pascoe in the first over after tea. Patil collapsed in the crease and had to retire hurt. Though still unwell, he batted in the second innings at the insistence of captain Sunil Gavaskar as India struggled to avoid an innings defeat.

Two weeks later, with a helmet on, Patil hit a spectacular 174 in the Adelaide Test. It came after India lost the first four wickets for 130 against the Australian total of 528. At the time the highest innings by an Indian in Australia, it took him just over five hours and included twenty two fours and a six over mid-wicket off Bruce Yardley. In the next series against New Zealand, Patil opened the bowling for India along with Kapil Dev in the Auckland Test.

Patil found himself out of the team after four Tests in the home series against England in 1981–82 but was picked for the away series that followed immediately after. Here in the Manchester Test he scored his second hundred. India was in some danger of following on when he added 96 runs with Kapil Dev a little over an hour. England took the second new ball soon after and Patil hit the last two balls of an over from Ian Botham for four and three. In the next over he hit Bob Willis for six fours (4440444, the third ball being a no ball) – "two cover drives, one flat batted back over the bowler's head, two square cuts of ferocious power and a mig