Aston Martin stand-in driver Nico Hulkenberg has conceded he was "hanging on" after a failed overtake led to a "downward spiral" during the Bahrain Grand Prix.
The German made another return to the F1 grid as a substitute for Sebastian Vettel, who had contracted Covid-19 ahead of the season-opener.
Hulkenberg out-qualified team-mate Lance Stroll but struggled to make inroads into the midfield from 17th, eventually finishing in the same position but last of those still running.
Assessing his first race since the 2020 Eifel GP, Hulkenberg said: "The beginning was okay but I was just hanging on.
"It was tough for me. Obviously, that was always the hardest part of the weekend.
"Once you are out of that mode of running with new fresh tyres and the limitations become more and you have to manage and understand the car a lot more, that was difficult.
"[It was] A big learning experience. We went okay but I tried to overtake someone, out-braked myself a bit into turn one and from there onwards it was a downward spiral.
"I got lapped quite soon and you just fall back and back more. It was what it was."
Mercedes-powered cars struggled for relative pace compared to the competition during the first weekend of the year, with all Aston Martin, Williams and McLaren cars occupying the bottom six positions in the race at one point.
Asked how much of a limitation the power unit was, Hulkenberg offered a detailed explanation.
He said: "We saw also with DRS sometimes I was not catching people. We seemed to be a little bit down on speed on the straights. We have seen that, too.
"In the grip-limited zones we also have some issues with the balance and the front and rear axle limitations."