The Spaniard finished with the peloton three seconds down on stage winner Primoz Roglic (LottoNl-Jumbo). Crashes took down riders entering the finishing circuit around 30 kilometres out and then again in the final kilometre, but Valverde stayed clear of the carnage and will make the start in Friday's queen stage healthy and in a strong GC position.
"The most important thing today was getting through the stage unscathed and in contention, and that goal was accomplished. The nerves were really high in the finale - that's why you saw so many crashes," Valverde said. "The team kept me well protected, always together at the front - that makes me calm and happy. I felt very good on the Vivero; a small split formed right at the summit and I could react and bridge back without any problems.
"Everything feels good at the moment, and we can't wait for Friday's stage, the real key before the time trial. Should everything go as expected, we'll be up there with the top guys. I don't know what my position will be, but we will be making things hard for the rest for sure."
Not everyone was quite as fortunate Thursday. Trek's Alberto Contador crashed, suffered a mechanical forcing a fast bike change on the final climb and punctured in the last kilometre, leaving him in rough shape and expecting a 'complicated' night.
"I didn't realize about any of Contador's crashes, because I was riding up front," Valverde said. "It's sad to see him fall, but that's cycling - crashes happen anywhere, even more so when you don't expect them, you never know how it's going to end."
Both riders will be expected to be in the mix Friday given the steep climb that closes out the stage. For his part, Valverde likes the look of the profile, and knows that it may give him a leg up in the GC battle.
"Regarding tomorrow's Arrate climb: I must say it's one that I like, as I have won at that finish, though it's true that I haven't raced over the new roads to the summit," he said. "Now it's a really demanding finale and it's going to be a really hard day.
"Hats off to Roglic for today's win. He's another candidate for the GC, though tomorrow's climb is a steep one and we don't know how strong he'll fare. We'll see. We better keep thinking about ourselves and focus on staying at the front when the moment comes."
The GC battle in the Basque Country remains tight ahead of the last two critical stages. Quick-Step's David de la Cruz has a one-second lead over Roglic with nearly 30 riders – including Valverde – all sitting on the same time a further two seconds back.
Valverde has won numerous stages and a few points jerseys at the Vuelta al País Vasco over the years, but never the overall title.