During his stay with Ajax, Olsen earned the nickname De Vlo (The Flea) due to his posture and his ability to twist, turn and jump to avoid tackles.

The next season, 1982–83, Ajax successfully defended the Eredivisie title, and also won the Dutch Cup to complete The Double, with also young players Jan Molby and Marco van Basten in the squad.

The game ended a draw, but even though Olsen scored in the penalty shootout, Denmark were eliminated when Preben Elkjær missed his shot.

Olsen moved from Ajax to England in July 1984, joining Manchester United for a fee of £350,000, signed by manager Ron Atkinson.

He scored a total of 24 goals for the Reds in more than four years at Old Trafford, including a hat-trick against West Bromwich Albion in a 3–0 Football League First Division home win on 22 February 1986.

[2] He succeeded Dutchman Arnold Muhren as United's regular left winger, at a time when foreign players were still relatively rare in the English game.

He collected an FA Cup winner's medal in 1985, when United beat Everton 1–0 in the final at Wembley, having ousted veteran Dutch midfielder Arnold Mühren on the left wing that season.

[5] During October 1986, Olsen had a training ground bust-up with midfield colleague Remi Moses and by the end of the month he was put on the transfer list by manager Ron Atkinson.

[6] Through his later years at Old Trafford, Olsen had a hard time adapting to the changing English game, and saw his footballing development stagnate.

After suffering a serious injury, he left Caen and retired in 1992, despite being offered the chance to return to English football with Blackburn Rovers and Nottingham Forest.

After recovering from the haemorrhage, Olsen visited Australia coach Guus Hiddink at the Australian World Cup preparation camp in Melbourne.