Britain's Lewis Hamilton has admitted that his brilliant start to his Formula One career has left even him stunned and surprised.
Tensions have been building between Hamilton and Alonso
Hamilton stormed to his second successive Grand Prix win on Sunday and now leads the drivers' championship by 10 points from Fernando Alonso.
Hamilton said: "It's just insane and I find it very, very hard to come to terms with everything.
"I don't think anyone expected me to do as well as I'm doing."
Hamilton led from pole to chequered flag in Indianapolis to hold off the challenge of team-mate and double world champion Alonso.
He said: "I have to be smart and realise that I'm running at the front and there is a possibility of winning the championship.
"But I still think it's far, far too early to even think about it or get any hopes up."
Hamilton said he was still trying to come to terms with his record-breaking success for a Formula One rookie.
"This is the pinnacle of the sport and to come in, I didn't expect anything.
"I never expected to but I hoped maybe I would get a podium at some point - but I've been on the podium for the last seven races."
McLaren expect the rivalry between their drivers to intensify after Hamilton once again edged out Alonso.
Chief executive Martin Whitmarsh said: "Do I expect more speculation about our guys and their relationship? Yes.
"The reality is when you have two competitive drivers they're always going to have a go at each other."
Twice during the race at the Motor Speedway circuit, Alonso tried to pass his rookie team-mate.
We were happy to let them race so long as their competition wasn't threatening our one-two finish
The Spaniard applied pressure on pole-sitter Hamilton off the grid but the Briton pulled away.
Then, midway through the race, Alonso caught up with Hamilton and the pair went side by side down the main straight before Hamilton again got away round Turn One.
McLaren boss Ron Dennis admitted watching his drivers fight so closely was nerve-wracking.
"Fernando pushed hard and caught Lewis and this created some tense moments on the pit wall," he said.
"We were happy to let them race so long as their competition wasn't threatening our one-two finish."
McLaren had insisted during the build-up to the US Grand Prix that they are giving preference to neither driver, despite Alonso's complaints that the English team favour Hamilton.
And Whitmarsh expects Alonso to fight even harder when the teams return to Europe for the French Grand Prix on 1 July.
"The reality is both our guys are winners, they want to win," he said.
"If Fernando got out of the car and said he was delighted Lewis beat him today, I would be very worried.
"Fernando is a phenomenal competitor, it's a long season and he's still aiming to win the world championship."