Lewis Hamilton asked to retire after being involved in a lap-one incident at the Spanish Grand Prix that relegated both drivers to the back of the pack.
After qualifying sixth, Mercedes started Hamilton on the medium Pirelli compound in a bid to extend the seven-time F1 champion's opening stint compared to every other driver who was on the soft tyres.
But the decision left Hamilton a sitting duck in the early exchanges with Magnussen attempting a bold pass around the outside of turn four, the same corner as Hamilton's infamous 2016 incident with then team-mate Nico Rosberg.
After both Hamilton and Magnussen were forced to pit, the Mercedes driver informed his team: "I would save this engine guys if I was you. Sorry"
Not ready to give up on the race, engineer Peter Bonnington replied: Lewis, we still feel we can achieve points here today. P8 maybe better."
The incident was quickly looked at by the stewards for causing a collision although they felt no investigation was necessary despite Magnussen's comments as the Haas driver said: "Lewis knew what he was doing. He ramped me."