Guglielminpietro's club career reached its peak at the Italian club A.C. Milan, where he shared the limelight with some of the game's most notable stars, such as Paolo Maldini, Demetrio Albertini, Roberto Donadoni, Alessandro Costacurta, Leonardo, George Weah and Oliver Bierhoff. On the final matchday of the season, Guly scored the opening goal in a 2–1 away win against Perugia that won Milan the 1998–99Scudetto. His play declined during the following seasons due to injuries, and he was transferred to different clubs around the globe, never recovering his top ability. His first port of call after leaving Milan was at rivals Internazionale whom he joined in 2001. He scored his first and what turned out to be his only goal for the club in a UEFA Cup tie against FC Brașov on 27 September 2001. In 2004, he won the Copa Sudamericana with Boca Juniors. After a short spell back in his youth clubGimnasia in 2005, he retired.
International career
At the international level, Guly was capped 6 times for Argentina, although he was unable to score a goal. He was a remember of Argentina's 1999 Copa América squad that reached the quarter-finals of the tournament, losing out to eventual champions and South-American rivals Brazil.
Style of play
Although he lacked pace as a winger, Guly was known, however, for his accurate crossing ability from the flank. Although he usually played as a wide midfielder, he was also capable of playing as an outside forward.
Coaching career
In June 2007, Guly was added to the coaching staff of cross-town rivals Estudiantes de La Plata, under coach Diego Simeone, with a third former Argentine international, Nelson Vivas, as assistant coach. Diego Simeone left Estudiantes de La Plata in December 2007 claiming a supposed lack of the club's commitment to sign appropriate reinforcements for the 2008 Clausura and Copa Libertadores. Guly also took up the same position with the same coaching staff at River Plate in 2008 and San Lorenzo in April 2009, where he also was the manager of the club's reserve team. Simeone and his staff, including Guly, resigned in April 2010. In June 2013, he was the assistant manager of Nelson Vivas, who Guly formerly had worked together with in the coaching staff of Diego Simeone. On 27 February 2014, Guly was appointed manager for first time, replacing Fernando Quiroz at Douglas Haig. Guly decided to resign on 21 July 2015. On 27 November 2015, he was appointed manager for newly relegated Primera B Nacional club Nueva Chicago. On April 3 2016 after a 2-1 defeat against Guillermo Brown he decided to resign, leaving the team in fourteenth place, after just ten games with a total of 3 wins, 3 draws and 4 defeats. Later in April 2015, he was appointed manager of Central Córdoba. He left the position already two months later. On 15 March 2017, he returned to Douglas Haig.
