Guardiola won Europe's top prize twice with the Spanish giants, first in the 2008-09 season and again during the 2010-11 campaign.
He has yet to win the competition since leaving the club, despite managing Bundesliga giants Bayern Munich before taking over at Manchester City, having reached the semi-finals of the competition on multiple occasions with the German side.
The 48-year-old has failed to get Manchester City into the last four during his time in charge of the English side, with Wednesday's failure against Tottenham the second year in a row he's seen his side knocked out at the quarter-final stage by a domestic rival.
And Dutch legend Gullit has pointed to the lack of superstar Lionel Messi as the real reason why Guardiola has failed to reach the heights he got to while managing the Argentine.
"It’s because he doesn’t have Messi," Gullit said on beIN SPORTS. "That makes a huge difference.
"He tried to do it with Bayern Munich. He was close every time, but he couldn’t do it.
"Winning the [Bundesliga] championship in Munich is not an achievement anymore because they win it almost every year.
"And I know that Pep, this is what he wants. He wants the Champions League and I feel sorry for him."
Gullit also pointed to the fact that Guardiola's team with Barcelona was not built by the manager, and had already seen Messi make his mark.
"Of course when he was with Barcelona he had an unbelievable team inherited from [Frank] Rijkaard, who Messi had already made his debut under," he said. "And then Messi became even more important. And Messi was vital in a lot of games for him when he was with Barcelona."
And the former LA Galaxy boss says that money alone isn't enough to put together a Champions League winner.
"You can’t buy a team to do it," he continued. "That’s what it is. And I really feel for him. I see this passion and I see what motivates him, and this is a huge blow for this team."