Player
David O'Leary was born on May 2, 1958 in Stoke Newington, England. He began his football career as an attacking midfielder, but soon moved back to the central defense. In 1975 he joined Arsenal from Dublin club St. Kevins after being spotted by scout Gordon Clark. At Arsenal he was met two other Dublin boys, Frank Stapleton and Liam Brady, but still he got so homesick that the club sent him back to Ireland every once in a while for six weeks of vacation. He soon became an important part of the Arsenal defense, and by the age of 21 he had already played over 150 games for the club. In his 18 years there, he played a record 558 league games and won two League Championships, two FA Cups, and two League Cups. In 1993 he left Arsenal for Leeds United, but he only played ten games there before he retired due to injury.
O'Leary's international career also started early; his first chance came in 1977 against England at Wembley. Through his career, he racked up 67 caps for Ireland. In the 1990 FIFA World Cup he became a hero when he scored from the fifth penalty kick against Romania to secure a spot in the quarter finals.
Manager
After retiring in 1993 O'Leary kept quiet for 3 years, but when George Graham became Leeds' manager in 1996 he called on O'Leary, who had played for him at Arsenal, as his assistant. When Graham left Leeds in 1998 to take the reins at Tottenham Hotspur, O'Leary was appointed manager. Once in control, O'Leary did for Leeds' youngsters what Bertie Mee had done for him 20 years before at Arsenal; gave them a chance. Players like Jonathan Woodgate, Alan Smith, Lee Bowyer, and Harry Kewell became key players, and Leeds became a contender for the Premier League title for the first time in years. Signings such as Robbie Fowler and Rio Ferdinand, who came from West Ham for a record £18 million in 2000, made the team stronger but still the title kept evading them. The team finished in the top 5 every season from 1998 to 2002 without ever finishing first or second.
In 2001, Woodgate and Bowyer were sued for a racist assault after they took part in the beating of Sarfraz Najeib, an immigrant from Pakistan. Both O'Leary and the club took a lot of heat because of the case even though O'Leary harshly reprimanded the two players. An all-white jury returned a controversial verdict that cleared Bowyer of all charges and sentenced Woodgate to do 100 hours of community service. O'Leary put both players back into the first team after the case, in spite of criticism from just about everyone except Leeds fans, who loyally stood by their boys.
Eventually, disappointment from the years before along with a dispute over whether Rio Ferdinand should be sold to Manchester United caused the Leeds Board of Directors to fire O'Leary in late June 2002 and replace him with Terry Venables. As of right now it is unknown where he will go next, although the latest rumors suggest he'll become Marcello Lippi's assistant manager at Juventus. I'll update this as soon as anything is confirmed.
Sources:
http://scripts.ireland.com/sports/soccer/ScManInfo.Cfm?prnumber=1010
http://www.terracebanter.com/Leeds.html
http://news.bbc.co.uk/sport3/worldcup2002/hi/tv_radio_coverage/newsid_1907000/1907658.stm
Catchpole's World Cup: Italy 1990