Former F1 race winner Ralf Schumacher has insisted Nico Hulkenberg must seek assurances over a turnaround in fortunes at Haas before committing his future.
Hulkenberg rejoined the grid this season after a three-year hiatus, during which he completed a number of substitute appearances for Racing Point and Aston Martin.
The German's appointment ahead of Schumacher's nephew Mick was questioned given his lack of running in recent years, but Hulkenberg's qualifying performances have more than put those concerns to rest with drives echoing the pace that underlined his reputation as a top driver during his previous stint in the sport.
Hulkenberg impressed to finish second fastest in qualifying at the Canadian Grand Prix, though he started fifth after being penalised for a red flag infringement.
But the VF-23 plummeted out of the points as Haas' worrying trend of poor rear-tyre wear saw Hulkenberg defenceless against his rivals.
Viewed by others:
What can Haas offer him?
Writing in his Sky Deutschland column, Schumacher said: "Nico Hulkenberg once again had a modest race after a strong qualifying session – that's very frustrating for him.
"Both he and Kevin Magnussen have the potential to finish in the points, but the Haas team has too many deficits. They have reached a point where they need to think about what needs to be changed and restructured.
"Haas is currently at the very bottom of the field, and that can't be the case in the long term.
"Team boss Guenther Steiner stated at the weekend that he was satisfied with the driver pairing. In doing so, he held out the prospect of another year for Hulkenberg. But the question is: What can Haas offer him?
"If I were him, I would first have it explained to me what steps are being taken to improve the situation because one thing is clear, if everything stays as it is – including personnel – then not much will change."