Alonso said he would be open to offers for next year if by late summer he had not been convinced that McLaren-Honda could provide a winning auto.
But a collision with Felipe Massa sent Alonso into the gravel at the first turn on Sunday and he could only finish 12th - the first time he has passed the chequered flag this year. 'Keeping the body active, ' he wrote, standing by his trainer Edoardo Bendinelli with tennis balls to hand.
"I have the hope that at this grand prix we had our problems on Friday so that on Saturday and Sunday everything will go well".
Alonso said: "The vehicle felt quite different, running this asymmetric set-up feels not normal to drive so you need to adjust with your mind-set going into the run and into the first corner".
"It's clear that in 2017 he's not going to win any championships here, so he's thinking about where he can win races in 2018".
"The weekend in general was positive for us". Alonso said after the humbling day. Collectively, McLaren's Honda F1 power unit has moved beyond mere "letdown" status into a full-on disaster, but he does appreciate all the work they do to try to get it to work.
McLaren-Honda boss Zak Brown said he accepted Fernando Alonso's challenge to give him a race winning auto for next year, and had no concerns at him leaving the circuit to play tennis after another engine failure.
Alonso will miss the Monaco Grand Prix in a fortnight's time as he heads to the United States for the Indianapolis 500.
As for the rest of practice, Lewis Hamilton was 0.029 seconds quicker than his Mercedes team-mate Valtteri Bottas in Barcelona.
Ferrari pair Kimi Raikkonen and Sebastian Vettel clocked the third and fourth fastest times, less than half a second off Hamilton's pace.
While he described qualifying seventh as "a surprise", he said the improved auto gave him confidence to attack. I'm happy with the team, but we are not winning. "It looks like it will be between them and us", Vettel said.
This is not unlike Alonso's teammate Stoffel Vandoorne's decision to hit the treadmill during the race when his McLaren blew up in Bahrain.
Following the race, when asked what he plans to do on the slight over, he joked sleep would high on his agenda as practice begins immediately on Monday.