Schumacher has been struggling to get back to the front on his F1 return
Red Bull's Mark Webber says Michael Schumacher's return should not be judged until after the next two races.
Schumacher, 41, has been off the pace of Mercedes team-mate Nico Rosberg in all four races so far after returning to F1 after a three-year retirement.
"After Monaco we'll know how his form really is," Webber told BBC Sport.
"He knows he's not going to just jump back in and start blowing people away. He knows he was going to have to get used to it. He's not that naive."
Schumacher begins the European leg of the 19-race season at the Spanish Grand Prix in Barcelona on 9 May with an upgraded car in an attempt to get him on level terms with Rosberg, who is second in the drivers' championship.
Mercedes have introduced aerodynamic upgrades, fitted the chassis Schumacher used during pre-season testing and lengthened the wheelbase to improve weight distribution.
Schumacher has won the Spanish race six times and Monaco five times, and Webber believes that the German legend's feel for the Princpality's street track will give him a chance to demonstrate his full potential.
"He'll feel a bit more at home at Barcelona and Monaco," Webber said.
"They're the sort of places, particularly Monaco, where you just plug Michael in and off he goes.
"If he's not going to be doing that this year, you can say he might be having problems coming to grips with the car.
"These cars change every two or three weeks let alone every four years, so he's coming back to such a totally different environment.
"The cars are totally different, the tyres, the aerodynamics, all of which he's had to get used to.
"He's going to have to work at it - and that's what he's doing right now.
"But as I always said, you have to take your hat off to him, it was a very brave call to come back and test himself again at the highest level. He's an incredible competitor and he always has been."
Schumacher has scored just 10 points this season and had his worst showing of the season at the last race in China, but he is hoping the changes to the car for Barcelona will help him up his game.
"Our step forward in Barcelona will be bigger than you can make at each race during the fly-aways but it would not be realistic to expect us to suddenly be competing right at the front," Schumacher said.
"I am hoping for a better race in Barcelona than I had in China and of course I would not mind having had better results so far.
"However, the good news is that after three years away, I am feeling extremely motivated."