Lewis Hamilton topped the opening practice session for the Italian Grand Prix as he sets about clawing back part of the 29-point deficit to Mercedes team-mate Nico Rosberg this weekend. Hamilton's time of 1:26.187 was 0.623s clear of nearest rival Jenson Button in the McLaren. The high-speed nature of the circuit means teams have arrived at Monza with low-drag aerodynamic configurations, and although Mercedes is still expected to dominate, McLaren managed to get both of its cars in the top five. Nico Rosberg was 0.808s off Hamilton, but still has plenty of time to close the gap ahead of qualifying on Saturday afternoon. Fernando Alonso was on typically good Friday form in the Ferrari, finishing the session fourth ahead of the second McLaren of Kevin Magnussen. Despite Renault's power deficit, Sebastian Vettel still managed to feature in the top six for Red Bull, although team-mate Daniel Ricciardo had to settle for 16th after a power unit issue midway through the 90 minutes. Kimi Raikkonen was seventh fastest in the second Ferrari ahead of Sergio Perez's Force India, which was looking increasingly skittish as the session wore on, but did register the highest top speed at 348km/h. Perez only took part in the second half of the session after handing over his car to Daniel Juncadella in the first 30 minutes to give the Force India reserve driver some Friday running. Several drivers missed their braking points at Turn 1 and continued through the run-off area, including Hamilton who managed a wave to the Tifosi as he did so. All the drivers avoided major incidents, although the new run-off at Parabolica saw some action, as did the gravel at Ascari when Perez lost the rear of his Force India on the approach. The Williams had a typically low-key start to Friday practice with its cars in 12th and 13th, but it is still expected to be genuine contender when the running becomes competitive on Saturday afternoon. Giedo van der Garde and Charles Pic both got outings in the Sauber and Lotus respectively, while Roberto Merhi made his F1 debut in the Caterham. Rather impressively, Merhi beat his team-mate Marcus Ericsson by 0.25s, although Ericsson did appear to have an issue towards the end of the session. Kamui Kobayashi will be back in the Caterham for the rest of the weekend.