A reporter once asked him why he chose 13 jersey. Barak replied, I'm not superstitious. When Leverkusen signed with me, the jerseys were only 13 and 15. I asked Waller, the technical consultant of the team at that time, which number he should choose. And 13 is the number he wore in Leverkusen for many years, so I chose this number. Everything went well from then on, so I'll keep this number.

When he joined Chelsea, Gallas' number was 13, and Ballack was told that he chose 19. However, Gallas did not return to the team in time according to the training time. Mourinho was furious and informed the team that Gallas' 13 jersey was removed from the store and handed over to Ballack. Gallas was very unhappy and left the team soon.