Sigurdsson was confirmed on Wednesday as Everton's club-record signing in a deal initially worth £40m but the protracted transfer negotiations with Swansea have impacted the 27-year-old's pre-season preparations.
So far this summer, Sigurdsson has played just 45 minutes of a friendly against Barnet last month. He pulled out of the Swans' pre-season trip to America once Everton's interest was firmed up with an offer and he also missed their Premier League opener against Southampton last weekend.
The Toffees face a stern examination at the home ground of title favourites City but Koeman says further assessment of his new acquisition's fitness will be required before he decides if Sigurdsson is able to play some part at the Etihad Stadium.
"We will do some tests to see how his physical state is but he told me he did training and played 45 minutes in a friendly at the beginning of pre-season," the manager is quoted as saying in the Liverpool Echo.
“Of course he needs game time but if it's game time then it will be with the first team. I don't know if he will be involved on Monday and we will make that decision on Sunday.”
Koeman altered his rhetoric on evertonfc.com today, indicating that he expects Sigurdsson to feature in each of the next three games before the international break.
“I'm not worried about his fitness," the Dutchman continued. "Of course, as a player you need game-time and need to play games in pre-season to get to 100 per cent. But his fitness is okay and he is a good professional.
“He will get time next week. We have a tough week coming up and he will be part of all the games next week.”