The seven-time world champion endured a difficult opening day of practice at Barcelona, as Mercedes had its first proper run on a regular circuit of new upgrades following their introduction in Monaco.
Hamilton ended second practice 11th fastest overall, 0.642 seconds adrift of pace setter Max Verstappen, with team-mate George Russell less than two-tenths quicker in eighth.
But with the fight behind Red Bull looking extremely close, Hamilton says that a lot of work is needed ahead of Saturday if he is going to get safely in to Q3.
“I think from the pace that I have today, it's a struggle for me currently to get into top ten,” he explained. “But hopefully, we'll do some changes overnight.
“I think it's very, very close between us in that P5 back to P10 [position]. It's impressive to see the improvements that everyone seems to have made all around us.
“If we look at [Esteban] Ocon, the Alpines are doing great. We saw the Aston Martin is second right behind the Red Bull, which is really, really impressive. So it's not going to be easy, that's for sure.”
Team-mate Russell was slightly more optimistic about the situation Mercedes found itself in, as he pointed out that the squad often faced difficult Fridays before its pace ramped up over the remainder of the weekend.
Source: Autosport