While Factory Yamaha rider Jorge Lorenzo left the Jerez MotoGP test believing he should have raced the softer rear tyre, Tech 3 Yamaha's Pol Espargaro came to a similar conclusion about his choice of rubber.
The reigning Moto2 champion joined only Valentino Rossi and Scott Redding in opting to race the hard front in Sunday's Spanish Grand Prix, but was left in a frustrated ninth.
Espargaro went on to set the seventh fastest lap at the test, compared with only the 13th fastest lap in the race.
"I'm really pleased with the work we've done today because after the race I was doubting some of the decisions we had taken yesterday, and luckily this test day gave us the opportunity to evaluate the modifications we wanted to try, including the other tyre option we didn't race on,” he said.
“As a result, I would say we made a couple of mistakes during the weekend, but this can happen when you are inexperienced, the important thing is we cleared our doubts and put ourselves in a much better position for the upcoming races.
“Today I've been able to ride with a much better rhythm. We improved my feeling with the front end of the bike and also on new tyres with the full fuel load, and I feel altogether more comfortable.
“Now I'm looking forward to the all-important team's home race in Le Mans where I'm really confident I can put on a great show for the French fans after today's improvements, especially considering that we've already been quite close to 5th during the race yesterday."
Team-mate Bradley Smith, who used the medium front and soft rear to finish eighth in the race, set the ninth fastest test lap time.