SONOMA, California – The night before Sunday’s GoPro Grand Prix of Sonoma decides the Verizon IndyCar Series championship, how do the top five title contenders sleep?

Four-time series champion Scott Dixon of Chip Ganassi Racing, known for keeping calm and cool amid the most extreme pressure, assured that getting shut-eye is never an issue.

But Team Penske’s Helio Castroneves begged to differ, albeit in a teasing tone.

“You’re nervous,” a playful Castroneves said to Dixon this week. “You get nervous.”

An amused Dixon smiled.

“I don’t,” he said. “I don’t know where he would get that information from.

“I can always sleep. I think the days leading up to the races are so long, you try to get through so much whether it’s commitments or on-track stuff, by the time you get back to the hotel, you’re pretty wiped out.”

Dixon is a close second in the points and his No. 9 NTT Data Honda will start sixth on Sunday. Castroneves, a three-time Indianapolis 500 winner in search of his first series title, is third in the points and his No. 3 Hitachi Chevrolet qualified fourth.

They’re all chasing points leader Josef Newgarden, whose No. 2 hum by Verizon Team Penske Chevrolet is on the pole. Newgarden, who leads Dixon by four points and Castroneves by 23, said he can convince his brain that this is just another race.

Teammate Will Power, a 2014 series champion, is never sure if getting quality sleep will be difficult on the eve of a race, but he won’t make it worse by worrying about it. Power’s No. 12 Verizon Chevrolet qualified next to Newgarden in second.

Defending champion Simon Pagenaud, who is fourth in the points and will start third in the No. 1 DXC Technology Team Penske Chevrolet, is typically unable to unwind after work.

“I don’t sleep after the race,” Pagenaud said. “That’s something that is getting worse and worse. Every race, I sleep less and less after the race. Even when I win, yeah.”

Castroneves suggested some competitive drivers don’t want to acknowledge night-before restlessness, presumably for fear of seeming vulnerable.

“If anybody says, ‘No, it doesn’t matter for them,’ even Scott Dixon who is the ‘Iceman’ in the series, they’re not telling the truth,” Castroneves said. “They’re hiding something. You’ve got to be feeling excited or (have) little butterflies in the stomach. You’ve just got to know how to deal with that. I feel when someone is like that, they’re sharp and ready to go.

“Any race, for me, it doesn’t matter if it’s the end of the season, the title, the finale, any race you get a little bit of the butterflies in your stomach.”

Pagenaud had trepidation before last year’s season finale, when he won from the pole to defeat Power for the championship.

“I remember being agitated the week before,” the Frenchman said. “We had a test the week before race weekend and it didn’t go too well last year. I had lots of thinking going on for a few days after the test, not knowing if we were going to be competitive enough. 

“This year, I’m more relaxed because I already have one in the bag. As someone’s life dream, that’s accomplished. Now I can focus on other things, being stronger and more aggressive.”

Power never knows what to expect when his head hits the pillow, but has learned this much: Don’t read too much into it.

“It just depends,” the Australian said. “Sometimes, I sleep really well and have a terrible day. Sometimes, I don’t sleep at all and have a very good day. Don’t know. I just don’t know. Sometimes, I think not sleeping well is actually better. It just means you’re more ready.”

Newgarden, who has won a series-high four races this season, suggested his mindset won’t be much different from the night before the series’ most prestigious race, May’s Indianapolis 500 presented by PennGrade Motor Oil.

“If you think of it as the Indy 500, which it is, then it can be difficult,” he said. “Now you’ve turned it into the Indy 500, which is a big deal. I think it will be the same for the championship. If you allow yourself to think, ‘Well, if this race doesn’t go right, you don’t win the championship. It’s the championship race,’ I think that can make it more difficult to think about.

“So, to me, I just think of it as another race. We go to a track every week and we try to win the race and we try to be as successful as possible, as fast as possible. That’s all we’re going to do. We’re just going to try to be as quick as possible and hopefully it’s enough. If it’s not enough, then it’s not enough. But we can only do so much. We can only do what’s in our control.”

When a reporter questioned Newgarden’s ability to entirely block out the significance of such an important race, especially for a 26-year-old driver in position to win his first series championship, the driver conceded he’s not perfect.

“You’ve got to control your thoughts, but you can only do that so well,” Newgarden said. “It’s not like I’m some (‘Star Wars’) Jedi.”

After winning the pole on Saturday, Newgarden admitted his mind wanders on what could happen next.

“You tell me not to think about it,” he said of winning a series title, “and you’re going to think about it.”

The GoPro Grand Prix of Sonoma to determine the 2017 Verizon IndyCar Series champion airs live at 6:30 p.m. ET Sunday on NBCSN and the Advance Auto Parts INDYCAR Radio Network.