Nico Rosberg believes Mercedes need to improve on their long runs after the likes of Williams and Red Bull showed good progress on Friday.
As expected, Mercedes were fastest in both sessions with Lewis Hamilton setting the pace in FP1 and Rosberg taking over later in the day.
It bodes well for qualifying on Saturday, but Rosberg admits they are starting to look over their shoulders in terms of the long runs following solid work by the likes of Valtteri Bottas in the Williams and Red Bull's Sebastian Vettel.
"Yep, all feeling okay, it's been a good day today," Rosberg told ESPNF1. "The others seem to be a little bit closer so we need work hard today to optimise everything tomorrow.
"Our car seems to be better on one lap than on the long run so it's long run that we need to work on to make sure we are quickest there. Everything is a bit closer so I think we still are looking very, very good but we need to work hard this evening to optimise everything."
The last four races at Monza have all been won by the driver starting in pole position, but Rosberg knows that the track offers plenty of overtaking opportunities so they can't just rest on their one-lap speed.
"I'm not into those statistics so much. Here qualifying is important but in the race you can overtake so it's important to be good at both," he said.
"Of course yes, the starting position is a big advantage and if we can keep the advantage we seem to have over one lap here then that would be great. In general I wasn't 100% happy with the car today, there's still some work to do tonight. In the long run it seemed that quite a lot of teams were quite a lot closer. It's balance that I need to work on this evening."