David Wagner hopes Jurgen Klopp can end Liverpool's wait for a Premier League title this season but acknowledges it will be tough in an "unpredictable" division.
Liverpool have not won the English top flight since the 1989-90 season, finishing just one point short of domestic treble-winners Manchester City last season.
The Reds claimed the Champions League - their sixth such triumph - but there is a desire to conquer the domestic league again.
Wagner is a friend and former colleague of Liverpool boss Klopp and will be supporting them in the coming campaign.
"I don't really believe, but I can hope Jurgen Klopp will go even further and win the Premier League title," he told Omnisport.
"But I know it's anything but easy. He will work very hard on it with his boys, but this league is so unpredictable.
"There are so many big games and then there are the games against those apparently 'small clubs', who are great, too. It is such a tough league.
"What Klopp has shown so far is incredible and I really wish for him to become [a] champion. But I don't know if it will actually happen."
Wagner left the Premier League as Huddersfield Town tumbled towards relegation last season.
He is now back coaching with Schalke, the bitter rivals of Borussia Dortmund, where he and Klopp were last united, but insists a return to the Bundesliga is not a backwards step.
"No, it's not a step back at all," he said.
"If I didn't want to do it, then I wouldn't have done it.
"Nobody said that I had to say 'yes' here. That was not the case. I wanted to have it that way.
"I do not see it as a step backwards either. But I do understand, and it's not a secret that the Premier League is currently the best in purely sporting terms.
"The number of top players there is outstanding and the coaches are of the highest quality. There's no denying that."Published 07 Aug 2019, 03:46 IST