Fernando Alonso has reflected that Aston Martin "cannot" judge its progress without the feedback of injured driver Lance Stroll.
Two-time F1 champion Alonso joined Aston Martin over the winter from Alpine, replacing the retiring Sebastian Vettel.
With pre-season testing limited to just three days this term, meaning just one-and-a-half days of running per driver, every minute of track time was critical.
Unfortunately, injuries sustained in a cycling incident ruled Stroll out of these sessions with his participation in the season-opening Bahrain Grand Prix now a doubt.
Given the Canadian's experience of last year's car and the inherent traits common to Aston Martin, Alonso said of his team-mate's absence: "It hurt a lot.
"I think we miss him because some of my comments or my feelings with the car, we never know if it is just me in a new team and a new car or whether it is just an Aston Martin thing that Lance could have spotted.
"Brake pedal feeling, power steering, all of these things - I don't know if it is a legacy from this team or it is just new to this car.
"We cannot do it without him so I hope he can come (back) very soon."