Seluk has been embroiled in a very public, 24-hour row with the Manchester City manager after Guardiola demanded an apology from the Ukrainian for his recent comments about the club.
"The team he took at Barca had been built by Frank Rijkaard and then he was lucky to have Lionel Messi," Seluk told the Daily Mirror.
"It was Messi who made Barca, not Pep. Luis Enrique has shown that Barca's success was not down to Guardiola.
"It was the same in Munich. He couldn't fail. My grandfather could have won the league with that team.
"If Pep wants to prove himself as a great manager, then he should go to Zaragoza or Sunderland. Let's see how good he is when he doesn't take over a great team and hasn't got half-a-billion pounds to spend."