Although the team remained in the lower part of the top 10 in Thursday practice, Button said his feeling with the troubled car on long runs was better than of late.
His only reservation was a fear that he would be too mired in the midfield to show that speed.
"The pace on the long run is surprisingly good," Button said.
"Not that that matters much around here when you're 1.2 seconds off the pace in qualifying...
"The problem is around here you have to qualify well, and that's our weakness at the moment. We just can't get the temperature in the tyre for lap one.
"There's a lot of hard work over the next few days to find out how we get the performance on the first laps, because we haven't got it yet."
Although McLaren has brought further upgrades for Monaco, Button believes the car is also simply behaving better with the set-up required for the street track.
"I'm happier with the car here than in the last few races," he said.
"There are some positives with areas that we've struggled in before, but seem a bit better.
"Because Monaco's such a different race, you change the car quite a bit, and it seems to be working a little bit better.
"We're still not setting amazing times, but I'm happier that we're going in the right direction and I think that we can improve on Saturday."
- Sports & Recreation
- Motor Racing