The 46-year-old Spaniard, who led Olympiakos to a domestic league and cup double in 2009 before an ill-fated stint with Villarreal in Spain, signed a one-year deal with the option to extend his stay for another season on Monday.
The club have yet to make an official statement but a media spokesperson confirmed to Reuters that Valverde would be presented at a news conference on Tuesday.
"What we hope is to bring Olympiakos back up to the level it was in previous seasons," said Valverde's assistant Jon Aspiazu in an interview with Skai radio. "The team is not in a good state at the moment.
"Above all, the team needs to believe in itself. There are quality players in the squad such as (Albert) Riera and (Ariel) Ibagaza. It needs patience, but what we need to do is to regain confidence."
Despite enjoying a successful single season in charge, Valverde fell out with then owner Sokratis Kokkalis but remained popular with the club's fans.
Kokkalis then embarked on a disastrous period of chopping and changing coaches with Temuri Ketsbaia, scout Bozidar Bandovic, former Brazil playmaker Zico and Bandovic again all managing the team before Lienen was appointed two months ago.
New owner Vangelis Marinakis was known to be unhappy with Kokkalis's appointment of Lienen days before selling his stake in the club and the German's failure to get the Reds into the Europa League playoffs prompted the shipping tycoon to dismiss him.
It was the first time in 19 years Olympiakos have exited Europe at such an early stage.
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