F1 car performance has taken a "huge" hit with the advent of the new technical regulations for 2019, according to a current technical director.
In a bid to improve overtaking, the FIA has mandated a raft of changes for this year, most notably to the front wing.
Force India technical boss Andy Green said he was shocked when the changes were applied in the wind tunnel.
"The whole thing throws us back about two years in development," he told Germany’s Auto Motor und Sport.
"I don’t know if we can even make it back to what we had before with these regulations."
Green recalls with particular horror the first time Force India tested the 2019 technical rule changes.
"The car looked really bad when we first put it in the wind tunnel," he said.
"The performance loss was huge. We are talking about several seconds in laptime."
Green said it will therefore be a very busy year for the engineers who are involved in developing the cars.
"The learning curve is very steep for everyone," he said. "I expect a long fight.
"Once the new season gets going, engineers will definitely be keen to see what solutions the competition comes up with."
As for whether the rules really will make overtaking easier in 2019, Green answered: "That’s not easy to say. But I’m already worried about it."