MONZA, Italy (AP) First it was physical contact.
Now it's turning into a psychological battle.
The fierce rivalry between the Mercedes teammates dominating Formula One took a new turn Sunday when Lewis Hamilton pressured Nico Rosberg into a mistake and overtook him to win the Italian Grand Prix.
''You have to be prepared for the unexpected,'' Hamilton said. ''I'm quite grateful for today that I didn't lose it, didn't crash into anyone on that first corner. ... I managed to keep my head.''
At the Belgian GP two weeks ago, Rosberg finished second after crashing into Hamilton early and sending his teammate out of the incident-packed race - resulting in disciplinary measures from Mercedes and a reportedly hefty fine for Rosberg.
The key event this time came on lap 29 of 53 as Hamilton had recovered from a poor start to pull up right into Rosberg's rear-view mirrors.
Feeling Hamilton's presence behind him, Rosberg braked hard and drove straight through the Monza circuit's first chicane at the end of the main straightaway.
Rosberg was slowed as he had to slalom through obstacles on the escape road, while all Hamilton had to do was stay on the track and he easily passed Rosberg.
Hamilton then cruised to his second win in Monza, his sixth victory of the season and the 28th of his Formula One career.
''Lewis was quick so I needed to up my pace and as a result I made a mistake,'' Rosberg said. ''It was very bad and that lost me the lead in the end. It's definitely very disappointing.''
Rosberg made the same mistake earlier in the race.
''It's not like many other races I've seen with Nico. He rarely made mistakes and two today in the same place,'' Mercedes executive director Toto Wolff said. ''Nico was under massive pressure from Lewis and Lewis deserved the win today.
Hamilton cut Rosberg's championship lead from 29 to 22 points with six races remaining.
Rosberg crossed 3.1 seconds behind, and Felipe Massa of Williams was third, a distant 21.8 seconds back.
Valtteri Bottas in the other Williams finished fourth and Daniel Ricciardo of Red Bull was fifth.
Hamilton started the season strongly by winning four of the opening five races then had a series of problems which allowed Rosberg to take over control of the championship. Now, Rosberg is the one having problems.
While they are both 29, Hamilton has more experience. He won the F1 title in 2008 by one point ahead of Massa.
''If you want to be a world champion you have to go through lows and highs,'' Wolff said. ''You need extreme mental strength to make it to the end and win the championship and I think both of them have that in them.''
For the second consecutive race, Rosberg was booed on the podium.
''Maybe that's something you also need to survive if you want to make it to the top,'' Wolff said.
It was a disappointing day for the Ferrari drivers before their home ''tifosi'' - fans - as Kimi Raikkonen finished ninth and Fernando Alonso's race ended on lap 30 due to a technical problem that resulted in the Spaniard pulling to a stop at the end of the main straightaway.
Ferrari dropped to fourth in the constructor's standings behind Williams in third. Mercedes holds a massive 182-point lead in the team category ahead of Red Bull.
Hamilton and Rosberg qualified 1-2 and fans had anticipated a battle between the pair at the first corner.
But at the start, Hamilton had a technical problem and dropped to fourth heading into the first chicane behind Rosberg, McLaren's Kevin Magnussen and Massa.
Hamilton rebounded by passing Magnussen with Massa's help on the fifth lap then overtook Massa around the outside through the first chicane on lap 10 and began to reduce Rosberg's lead lap after lap.
Meanwhile, Rosberg lost time when he drove straight through the first chicane on lap nine - a harbinger of things to come.
The layout of the Monza track - long, high-speed straights followed by slow corners - requires heavy braking.
''It's one of the most difficult tracks for braking because of low downforce and the highest speed of the year,'' Rosberg said. ''But that isn't any excuse or anything, that's just the way it is. ... Unfortunately I got it wrong two times in the race.''
Hamilton also had a problem 15 minutes before the race started, when a team mechanic dropped a portable brake cooler on his front wing, breaking it slightly and forcing a change.
''I came here with a positive attitude and hoping just for no issues,'' Hamilton said. ''I had another serious one but I managed to pull through it. I'm still looking for one of those weekends where we don't have any of those troubles.''
The Singapore GP in two weeks is up next.
Associated Press reporter Daniella Matar contributed to this story.
Andrew Dampf can be followed at www.twitter.com/asdampf