Jenson Button has downplayed his pace from Friday's first practice in Spain, saying it was his P7 in the afternoon that was more indicative of McLaren's form.
The British driver finished second quickest in the morning's session only slower than former team-mate Lewis Hamilton.
However, in the afternoon, as the track temperature rose to 45'C, Button was unable to repeat that feat.
The McLaren driver posted a 1:27.811 to finish seventh quickest, over two-seconds slower than Hamilton's best.
The 2009 World Champion, though, says he wasn't surprised to fall off the pace.
"The afternoon was where we expected to be," he told Autosport. "This morning was good and we were quicker than expected.
"I don't think it's anywhere near as good as it looked in FP1.
"The hotter temperature this afternoon was a lot harder for us to get the car working in.
"We seem to have a very small temperature range. So on both the short runs and long runs, we were struggling more.
"This morning we looked a lot quicker maybe because of temperatures and fuel loads."
Button, though, is refusing to rule out a recovery, confident there are steps McLaren can take this weekend to find a better balance.
"There are a few things on the car that I think help the balance and put us back into the fight with Force India and Williams, but everyone's behind Mercedes and we're obviously behind Ferrari and Red Bull.
"The first three teams have big gaps between them and they're a lot faster than us. And that's a pity.
"There's more we can do overnight for long runs, but short runs look more tricky."