Miller started from fourth on the grid on Sunday, the best of the rest as Yamaha once again dominated qualifying and locked out the front row.
The Aussie was in podium contention in the early stages of the MotoGP™ race in Barcelona before tyre degradation saw him lose touch with the pace at the front.
"I did a good race, but I wasn't fast enough," Miller said.
"I made a mistake in Turn 10 during the first lap and I lost time.
"But anyway, I got points, and now I will take some rest and I will focus on Le Mans."
Miller is sixth in the 2020 MotoGP™ standings, 33 points behind Petronas Yamaha's Quartararo.
Meanwhile, Miller has donated the visor tear-off strip that ended his race prematurely at the Emilia Romagna GP to charity.
Miller returns to the track in a fortnight for the French GP at Le Mans on 9-11 October.