The Danish driver replaced the axed Nikita Mazepin at the Haas F1 team amid Russia's invasion of Ukraine, with the deal being announced on the eve of the second pre-season test.
Haas then missed the opening morning of the test in Bahrain due to freight transport delays, only to regain the lost time through additional running time permitted later in the Bahrain test, resulting in Magnussen having a total of just one day of testing time to get up to speed in the new Haas F1 car.
Despite playing catch-up, Magnussen starred in qualifying for the Bahrain GP with seventh place in Q3 even though he suffered a hydraulics issue during Q2, which also forced him to stop on track at the end of the pole shootout session.
Reflecting on the last two weeks, Magnussen has been thrilled by the turnaround and while reliability concerns still remain he is confident of fighting for points in the opening round of the year.
"It's been a massive rollercoaster from getting the call from Gunther [Steiner], getting really surprised by that, and then trying to make it happen," Magnussen said on Sky Sports F1.
"There was some obstacles that I had to sort out and that was already a bit nervous.
"Then getting here, driving the car for the first time, having a sore neck and you hope the car's good but you never really know with F1 testing and then having an issue in qualifying, not thinking we could get out in Q3 - what a rollercoaster.
"I feel so unbelievably lucky to be in this situation that I'm in with a good car in Formula 1 - it's a lot of fun.
"We had some good long-run pace in practice but you don't really know what people are running - power, fuel and stuff - and it certainly wasn't bad on the long run either.
"Starting P7, if you can do that, you've got to go for points. The biggest concern is reliability, I would say, but fingers crossed we can get there."
Magnussen also said Haas F1 team boss Steiner had made no guarantees about the US squad's expected potential or performance levels for the new season, having left the team and F1 disillusioned with fighting at the back of the grid in 2020.
"He didn't promise anything - which he could've easily done that," Magnussen said. "They had some good feeling about what they've done with the car but, after Barcelona, there wasn't much to show for it.
"We were talking about it and he said that they think they have a pretty decent car but he didn't promise anything, so it's just crazy."
