Eric Boullier has apologised to Jenson Button for all his Friday troubles which resulted in the Brit covering just 17 laps in Bahrain.
Button managed just two laps in the afternoon session before an electrical problem caused a spin at Turn 1.
Out of the action for the remainder of the session, he emerged late in FP2 and again was forced to stop, this time after three laps.
His car recovered to the pits, Button was able to cover more laps later in the session, finishing the day with 17 to his name.
It was in sharp contrast to Fernando Alonso's day as the Spaniard covered 40 laps in total and was 12th quickest.
"On the one hand, Fernando enjoyed a trouble-free morning followed by an equally unproblematic afternoon, running through his planned programme without mishap," said Boullier.
"On the other, Jenson was forced to endure a frustrating day, the result of not one but two major interruptions, compromising his ability to complete satisfactorily not only FP1 but also FP2.
"We apologise to him for that."
As for what McLaren can expected for the rest of the Bahrain weekend, the Racing Director is hoping Alonso's P12 is a sign that McLaren-Honda are moving forward.
"It's too early to say where we are, pace-wise, but Fernando's best FP2 lap-time was 1.5s off Nico's [Rosberg] FP2 benchmark.
"That isn't where we want to be; having said that, I believe it demonstrates that our progress, although not always linear, is nonetheless directionally positive overall."