The Dane failed to get out of the first part of qualifying, while Romain Grosjean went all the way through to Q3, qualifying in P8.
Despite the relative slowness of his Haas, Magnussen did not seem to have an answer for the lack of pace.
“I don’t think anything special happened. We just don’t have the pace this weekend, so it’s really strange,” Magnussen said.
“I don’t have any answers as to why we are lacking so much pace.
“One second [from team-mate Grosjean’s best Q1 time] is like a light year.
“Sometimes it is the difference between pole position to Q3, so it’s very strange and we need to see if we can find some answers.”
When asked further about where the car was lacking pace, the Dane again had no answer, adding that it was just generally slow on Saturday.
“It’s not just one place, just an overall lack of performance,” he continued.
“The car is somewhat balanced, so there is no answer really. We need to look into properly and try to understand.
“It looks like it is going to be a tough day [on Sunday] so we will try to take what we can.”
Magnussen will start Sunday’s Singapore Grand Prix in P16, while his Haas team-mate, Romain Grosjean, lines up in P8.