Palace won this preseason friendly 3-1 in Tampa.
Lopetegui told whufc.com: "Tonight was to show us that we have 15 days in front of us to keep on working very hard and to try to evolve the players we have as soon as possible, and the new players, too.
"We have 15 days to keep working and keep going to put the team in the best way for the first step that is, of course, the first Premier League match against Aston Villa.
"Of course, we have to improve on a lot of things and I think maybe more or less the same as the Wolves game, until 60 minutes we have been balanced in the match.
"After, we have to analyse and ensure we are able to do better, to defend better and don’t concede easy goals. I think we have to change this.
"We are working hard and we know that we have worked very, very hard, so it’s possible that the legs were a little bit tired, so I think we have two days until we go back to London, then we will start the new week with new energy knowing that we have one other friendly match in our stadium to be ready for the key date which is Aston Villa.
"We have to progress and we need to progress for sure.
"There are good things. For example, Michail stayed in the pitch for 60 minutes and it’s good for him, so we are increasing the minutes for certain players.
"Of course, this is a good thing, but they arrived late, so we have to try to take advantage of these days to put all of them in the best way and to analyse how we are going to train the new players who are waiting for us in the next weeks."