Donadel is a youth product of Milan, playing for the youth side between 1998 and 2002, winning the Torneo di Viareggio in 1999 and 2001 before being promoted to the senior side. On 4 March 2001, he made his debut for Milan, coming on as a substitute for Andres Guglielminpietro in the 78th minute of a home Serie A game against Parma.[2] The following season, he made his debut appearances in the UEFA Cup and Coppa Italia.
Having made just 4 appearances for the senior squad of Milan, Donadel was loaned out to Lecce in July 2002.[3]
In June 2003 Donadel was sold to Parma in a co-ownership deal for €2 million.[4] (with 50% rights of Roberto Massaro was purchased by Milan for €2 million[4]) The deal made Milan making a profit of €3.897 million.[4] In June 2004 Milan bought back 50% rights of Donadel for €800,000[5] in a four-year contract (Milan booked the contract value of Donadel was €4 million instead of €1.6 million, thus receiving €1.2 million financial income[6] instead of costing Milan to write down the value of retaining 50% registration rights for €1.2 million.) In 2004–05 season Donadel was loaned to Sampdoria[7] for free[6] and finally Fiorentina in January 2005, for €200,000.[8]
After a successful half-season-long loan with Fiorentina, he was signed permanently for €1.2 million in a four-year contract.[8] The deal also made Milan book a €1.8 million loss.[9] as the residual value of Donadel's contract, after amortization, was €3 million. In 2005–06, he was a regular for coach Cesare Prandelli, who had already appreciated the skills of Donadel, as they were together at Parma. In June 2007, he was offered a new contract until June 2011.[10]
On 24 June 2011, he signed a four-year contract with Napoli. During his stay with Napoli, he only appeared in four league matches and during the 2013–14 season, he was sent on loan to Verona, where he was a regular starter for the club.
Once his loan spell with Verona concluded, Donadel went on trial with Major League Soccer side Montreal Impact. Donadel officially signed with the Montreal Impact on 1 December 2014.[11] His 30-yard strike in a 3–0 home win against Columbus Crew, on 11 July 2015,[12] was voted MLS goal of the week for the 19th week of the 2015 MLS season.[13] On 25 October, he assisted one of Drogba's goals as the Montreal Impact came from behind to defeat domestic rivals Toronto FC 2–1 at home; the win gave Montreal the home advantage for their knock-out fixture against Toronto in the 2015 MLS Cup Playoffs.[14]
Donadel was waived by Montreal on 22 June 2018.[15]
On 17 December 2021, Donadel was announced as the new assistant coach of Spartak Moscow, following the appointment of Paolo Vanoli as the club's new head coach.[17]
On 11 April 2023, Donadel took on his first head coaching job in charge of Serie C club Ancona.[18] He was dismissed on 23 October 2023 due to negative results.[19]