Jenson Button will almost certainly start the Monaco Grand Prix at the back of the grid due to a 15-place penalty which is set to be imposed for changes made to his McLaren's power unit.
Button was already expected to be up against it this weekend, but his task will be even bigger after alterations were made to the MGU-H element and turbocharge of his MCL32.
It is the fifth time engine changes have been made to a car usually driven by Fernando Alonso, who is competing in the Indianapolis 500 this weekend, so a penalty is due to be incurred by 2009 world champion Button.
McLaren racing director Eric Boullier said: "It's awful for Jenson and awful for McLaren and not expected at all. But it's Monaco, so we'll try anything we can."
Stoffel Vandoorne, Button's team-mate for the weekend, has already been hit with a three-place grid penalty for causing a collision with Felipe Massa in the Spanish Grand Prix.
McLaren have endured a miserable season, failing to earn a solitary point from five races.