Carlos Sainz was celebrating his 23rd birthday on Friday, but he didn't have much to celebrate following second free practice for the Italian Grand Prix.
Sainz had already been handed a 10-place grid penalty for taking his fifth MGU-H. He now looks set to sink even further down the grid at the Autodromo Nazionale Monza this weekend.
Midway through the afternoon session, he was 11th fastest on the time sheets when his STR12 suddenly started belching smoke and oil.
"Not the birthday I wished for!," sighed Sainz after the early end to his day.
"I knew since yesterday that we were going to get a grid penalty for changing part of the power unit. That wasn't a surprise. But today's PU issue is definitely not something we welcome!
"This didn't allow us to complete our programme and we know that we're up for a very difficult weekend here in Monza.
"We will of course keep our chin up and keep pushing," he added. "I have to say I'm feeling good in the car. It's very light as we are running very low downforce to try and compensate our engine deficit.
"It's tricky out there, but at least I'm enjoying it and hopefully we can extract the maximum out of the car tomorrow and on Sunday."
Sainz' team mate Daniil Kvyat was also unhappy with how the day went. He complained about the car's handling, and was received an early recall to the garage after engineers detected a problem.
"Not a good Friday," summarised the Russian. "I didn't feel comfortable in the car today. Nothing really worked as well as it should have.
"We now need to review everything overnight, understand the reason for this and hopefully find a better solution for tomorrow."
Toro Rosso's head of vehicle performance Jody Egginton elaborated on his drivers' reports.
"Carlos was able to find a reasonable balance and set representative times on both compounds," said Egginton. "[He] set representative times on both compounds. Unfortunately his day was ended early with what appears to be a power unit failure.
"Daniil was less happy with the balance of his car early on in the session," he reported. "A further set up change was evaluated before he switched to longer runs. However, we also had to end this run slightly early due to a potential reliability issue.
"Frustratingly, we have not been able to gather a lot of tyre data from the long runs today," he added. "In the case of Daniil we also have some further work to do to optimise his set up. However, on the flip side, with Carlos we have managed to move forwards with the set up."
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