The two became embroiled in a bitter feud during the club's pre-season tour of America and had to be separated by team-mates.
Shorly afterwards, the Brazilian's record breaking €222m move to French giants PSG was confirmed, something which Semedo believes played a big role in their falling-out.
'It was a normal training situation, but it went to another level. It did not affect me because I had the support of the whole team and my friends,' Semedo told Spanish publication 'Mundo Deportivo'.
'I had just arrived and one of the most influential players on the team came into conflict with me after a normal training situation.
'It bothered me at the time, but I also managed to understand: he was in a difficult time, he wanted to leave.'
It is thought that Neymar was unimpressed with a challlenge made by Semedo during the session and stared down his new team-mate, before Sergio Busquets had to step in and restrain the Samba star.
Neymar promptly stormed out of the training session, though it is thought that the pair swiftly exchanged apologies and were pictured embracing after the 3-2 friendly victory over arch-rivals Real Madrid in late July.