In 2018, Ricciardo announced a shock decision to depart the energy drink team and join Renault, who was considerably less competitive in the Formula 1 field.
Ricciardo won seven grands prix in his five years with the energy drink team, joining in 2014 as a replacement for compatriot Mark Webber.
The Australian brought a lively personality to the team and was consistently cracking jokes during his time there, forming a publicly lighthearted relationship with teammate Max Verstappen.
"The atmosphere in the team is good, but it is not as jovial since he went," Marko told Motorsport-Magazin.com.
"He is also one of the fastest drivers and can catch up excellently when he needs to. And his jokes are also missed."
After half a season of difficult races and disappointing results, Red Bull promoted rookie Alexander Albon to the team, who scored top-six finishes in all races bar Brazil, where he was set for a podium finish before he was involved in a collision with Lewis Hamilton.
Marko praised Albon's efforts in the second half of the year with the Milton Keynes based oufit and is hopeful that the Thai racer will enjoy a strong season in 2020.
"Alex has done very well," Marko said. "He joined the team without having tested the car and he was in the points at every race except Brazil, where he was hit by Hamilton.
"He is self critical and knows where he can improve and it is all very positive. We hope that he will be a good teammate for Verstappen this year."
Bahrain International Circuit - Winter testing