Aprilia MotoGP boss Romano Albesiano believes the team is still "suffering the consequences" of signing rookie Sam Lowes for 2017.
Lowes graduated from Moto2 to join Aprilia's fledgling MotoGP project last year, but his two-year deal was terminated early amid a string of poor results.
He returned to Moto2 this year and was replaced by Scott Redding, who has likewise struggled aboard the RS-GP and has failed to retain his seat for the 2019 season - with Andrea Iannone signed to take his place.
Albesiano admits Aprilia made a mistake in choosing not to retain one of its 2016 riders, Stefan Bradl and Alvaro Bautista, to join Espargaro for '17 instead of picking Lowes.
"I admit that from this point of view it was an error," Albesiano told Gazzetto dello Sport. "The main error was to bet on a young rider when the bike wasn't at the right level.
"The problem was not replacing both [Bradl and Bautista], Aleix gained a second when he got on the bike, but having another experienced rider in the box would have been better.
"From this point of view we are still suffering the consequences."
With eight races left to run in 2018, Aprilia finds itself sixth and last in the manufacturers' standings - trailing '17 newcomer KTM by 13 points.
Espargaro's best result of the season has been a ninth place at Le Mans, with Redding having failed to finish any higher than 12th.
The British rider endured a particularly miserable weekend in Austria, where he lambasted his Aprilia machinery after qualifying and finishing 20th on a weekend when he had starred in wet practice.
He subsequently apologised for calling the RS-GP a "piece of shit" and Albesiano said the matter is now closed - calling it "a moment of blackout, in which he let himself go to unpleasant things" but adding "he apologised and the matter ended there."
Aprilia is testing at Misano this weekend, along with Ducati and Yamaha.