Career
Kirev was a part of Bulgaria national under-21 football team Youth career
Kirev started playing football in the little amateur club Football Club Germanea from Sapareva Banya. His first coach was Georgi Stanchev.
At the age of fourteen he started training in the junior team of Slavia Sofia.
Slavia Sofia
In August 2007 Kirev signed his first professional contract with Slavia. He made his competitive debut for the club on 25 April 2008 against Spartak Varna in the twenty five round of the Bulgarian top division.
In next season (2008-2009) Kirev was the first choice for goalkeeper of the coach Stevica Kuzmanovski. He earned 7 appearances playing in the A PFG. Juventus
In December 2008, Kirev was invited by Serie A side Juventus to join trial period.
On 30 January 2009, he signed a four-and-a-half year contract.
In the following days Kirev was loaned for six months in the Swiss team Grasshopper Club Zürich. In June 2009, he returned to Juventus. However he started for the clubs Primavera youth squad helping lead them to a second consecutive Viareggio Championship.
In February 2010, Kirev signed for Football Club Thun in Switzerland, in attempt to gain first team experience.
On 1 July 2010, Kirev returned to Juventus and became the 5th keeper, behind injured Buffon, new signing Marco Storari, Alex Manninger and new signing Marco Costantino. He was called up to the first team, for the first time on 29 October 2010, against Milan.
In September 2011, Kirev joined Romanian Liga II side Politehnica Timișoara on a season long loan deal. He returned to Juventus on 1 July 2012.
On 6 July 2013 - Mario played in a friendly for Slovak side MFK Kosice against Hungarian side Debrecen, with MFK Kosice winning 4-1.
This could signal a move to Slovakia and the end of his Juventus career. From August 2008 Mario is a part of Bulgaria national under-21 football team and he is the only player on the team plying his trade outside of Bulgaria.
