In January, it was announced that Steiner would be departing his role as Team Principal at Haas ahead of the 2024 season following a poor campaign last term where the team finished last in the Constructors' for the second time in three seasons.
Steiner was instrumental in the founding of Haas, taking the model to US manufacturer Gene Haas with the team debuting in 2016, and was replaced by engineering chief Ayao Komatsu.
The team has revealed its first post-Steiner machine, the VF-24 for the coming season, with Hulkenberg admitting he was shocked at Steiner's departure.
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Hulkenberg on Steiner departure
"I got a phone call from Gene between Christmas and New Year," Hulkenberg told Sky Sports Germany.
"He informed me of his decision, which was surprising, I didn't expect it and didn't see it coming at all.
"I have spoken to Guenther since several times, and talking to him is always fun. I have a good relationship with him, both professionally and personally - he was the one largely responsible for my comeback [to F1].
"He opened the door for me, and partly for that reason, I regret he is gone, but it is Gene Haas's decision, and we will just move on.
"[Guenther] made such a great contribution to the team commercially, and it is no secret that the Netflix series became such a huge success, partly to him.
"We are going to miss him, he built all of this, as Haas was his concept, his business plan and his departure will leave holes we will have to fill - but we have to start rebuilding.
"That is where our focus is now."