A deal for former Haas and Sauber Formula 1 driver Esteban Gutierrez to race in the FIA World Endurance Championship with the DragonSpeed LMP2 team has failed to come to fruition.
The Mexican, who raced in both Formula E and IndyCar last year, had been on the verge of signing a deal with the American team for the 2018/19 WEC superseason.
DragonSpeed entered Gutierrez for the official WEC Prologue pre-season test at Paul Ricard in April, only for the deal to fall through last week.
Team boss Elton Julian told Motorsport.com: "We thought it was done and were having driving suits made and planning a seat fitting.
"Unfortunately it's not going to happen, which is a shame because it would have been exciting news."
Julian revealed that he still expected to sign "another ex-grand prix driver" for one of the vacant seats in DragonSpeed's Oreca 07 alongside sometime Champ Car driver Roberto Gonzalez.
"I'm confident that we are going to have a quality line-up, because our ambition is to win back-to-back titles in the ELMS and the WEC," he said.
Aubry, Tan, Jeffri join DC Racing for Prologue
Formula Renault Eurocup frontrunner Gabriel Aubry will drive for the Jota-run Jackie Chan DC Racing LMP2 squad at the Prologue test.
The Frenchman raced for the team in LMP3 in last winter's Asian Le Mans Series and will drive in GP3 this season for Arden, which has close links with Jota.
Weiron Tan, who was a race winner with DCR in the 2017/18 ALMS, is also listed to drive one of the squad's pair of Oreca 07s, as is ex-Formula 2 driver Nabil Jeffri.
DCR has yet to confirm that Aubry, Tan and Jeffri will race for the team in the WEC superseason alongside previously-announced signings Ho-Pin Tung and Jazeman Jaafar.
Elsewhere on the Prologue entry list, the Rebellion Racing squad had entered just one of its new Gibson-powered R-13s privateer LMP1s for the Prologue.
The first of the Oreca-developed cars is scheduled to be completed in the run-up to the test.
DragonSpeed's BR Engineering BR1, also powered by the Gibson V8, is also due to be ready to run in the week of the test.
Former Supercars frontrunner Alex Davison, who finished second in GT2 in the 2008 ELMS, is listed to drive Gulf Racing UK's new Porsche 911 RSR.
Tom Blomqvist has been entered in one of the factory BMW M8 GTEs at the Prologue alongside the MTEK team's six race drivers.
13 cars sign up for night test
A total of 13 of the 35 registered cars for the Prologue will take part in the full 30-hour test that includes night-time running.
These include Rebellion and ByKolles' sole LMP1 entries, one of the two Toyota TS050 Hybrids, both SMP LMP1s and a selection of GTE entries - including one BMW, two Porsches and one Aston Martin.
None of the seven LMP2 cars present at Paul Ricard will take part in the night session.