Early in his career, Zavec was briefly signed with Don King, but returned to Europe after the legendary promoter was unable to secure him bouts.

[7] On September 4, 2010, Zavec defended the IBF welterweight title the second time against mandatory challenger Rafał Jackiewicz at the Stožice Arena in Ljubljana.

[8][9] Zavec was expected to face the winner of Randall Bailey-Said Ouali IBF title-eliminator that took place December 10, 2010, but the bout was ruled a no-contest.

On February 18, 2011, Zavec defended the IBF welterweight title for the third time against #15-ranked Paul Delgado, performing again at the Stožice Arena, in front of 12,000 spectators.

After discussions to fight Paulie Malignaggi on the Saul Alvarez-Ryan Rhodes undercard fell through,[10] Zavec traveled to Biloxi, Mississippi to face former WBC light-welterweight champion Andre Berto on HBO on September 3, 2011.

Despite being a 4-to-1 underdog coming into the fight, Zavec proved competitive; trading clean punches with Berto and earning praise from HBO's Roy Jones Jr.