DeFreitas went to Willesden High School, in London, where he played football and cricket. He had trials at Luton Town F.C., but although offered an apprenticeship, wanted to play cricket.

DeFreitas made his first-class debut for Leicestershire in 1985 against Oxford University and recorded the startling bowling analysis of 3.4–2–3–3 as the students collapsed to a humiliating 24 all out. The following year he had a wonderful season, taking what was to remain a career high of 94 wickets and scoring his maiden century (at number 9) against Kent, and he was selected for the successful Ashes tour in 1986/87.

In the course of his 21 seasons in first-class cricket, DeFreitas had a somewhat nomadic county career, playing for Leicestershire from his debut in 1985 until 1988, then Lancashire from 1989 to 1993, and Derbyshire from 1994 to 1999. In 2000, he returned to Leicestershire, averaging over 45 with the bat that season, and captained the side in 2003 and part of 2004. He also played for the South African side, Boland, in 1993/94 and 1994/95.

DeFreitas announced in April 2005 that he would retire from cricket at the end of that season. This meant that had England not beaten the Australians that summer, there would be no remaining Englishmen in first-class cricket who had played in a victorious Ashes side, but this did not happen. On hearing the news, Mike Gatting, who had captained that 1986/87 team, told the BBC: "He's one of those guys you want in the game. It's sad he's going to retire but he's been good for the game." DeFreitas has the honour of being the 100th player in test cricket to take 100 wickets.

He remained part of England's plans until the advent of Dominic Cork in the mid-1990s, but was generally much less successful abroad than at home. His two best Test series were in 1991 against West Indies and, in 1994, against New Zealand, when he took 22 and 21 wickets respectively. His top Test score of 88, during which he hammered Craig McDermott for 42 runs off three overs with the new ball, helped England to a win against Australia in Adelaide, and earned him the Man of the Match award. DeFreitas was named as a Wisden Cricketer of the Year in 1992.

Defreitas also played the 1987 World Cup, but he, on the other hand, during the match against West Indies played in Pakistan as part of the 1987 World Cup, had to stop in the middle of his run-up in order to vomit. He had not been feeling well and the searing heat had made the affliction worse. Anxious not to lose his place, he had not mentioned his illness to the captain, preferring to try and see the day through instead. He managed this, without compromising his teammates.

Most would probably agree that DeFreitas never quite reached the heights his early promise suggested he would attain. In one-day internationals, DeFreitas seldom let England down – but bowled more economically than penetratively until his second Australian tour. In the World Series Cup that season, DeFreitas was often punished by the powerful Australian top order particularly Dean Jones. He performed creditably despite a persistent groin strain in the World Cup of 1992 but form was beginning to desert him by this stage. He was notoriously thrashed all over the ground by Sanath Jayasuriya in the 1996 World Cup quarter final – by no means alone – in a game where England were thrash