Blum reached the peak of national athletics in his first year as a senior by winning the 60 m title at the 2007 German Indoor Athletics Championships. This led to his first senior international call-up and he was a semi-finalist over that distance at the 2007 European Athletics Indoor Championships. He ran in three events at the 2007 European Athletics U23 Championships: he was seventh in the 100 m final but failed to finish in the relay and 200 m. He did manage third place in the 2007 European Cup 100 m, however. He improved his personal bests over all distance that year: 10.26 seconds for the 100 m, 20.85 seconds for the 200 m and 6.59 seconds for the 60 m.