And he believes Leigh Griffiths has boosted his chances by making a lightning start to his Celtic career following his January move from Wolves.
Griffiths was called up to the Scotland squad for the friendly against Poland on Wednesday, following the withdrawal of Grant Hanley and Robert Snodgrass, during a weekend in which he hit his first hat-trick for Celtic.
But McGhee warned that he would need to maintain his form up to the start of the European Championship qualifiers, which begin for Scotland in Germany on September 7.
"There's a fairly limited number of players we feel are going to be good enough to help qualify us," the former Celtic and Scotland striker said.
"Leigh Griffiths is one of them and we think that with Leigh Griffiths being at Celtic, and the new experience he will have in the Champions League, can only make him a better player and more prepared for the national team.
"It's fantastic he went to Celtic and that can benefit the national team.
"He's got a great chance at Celtic because they do provide him with chances.
"He has obviously risen to it and hit the ground running. We would expect him to get a lot of goals between now and the end of the season, and then it will be about the start to the season.
"Maybe (Craig) Mackail-Smith might be fit by then, and we have got Ross McCormack, Steven Fletcher, Leigh Griffiths, Jordan Rhodes.
"It's not about who is playing well now, it's going to be about August and September and how they are looking then."
McGhee could add Steven Naismith to his list given the Everton player has played in the lone striker role several times for Scotland in recent games.
But manager Gordon Strachan now has Steven Fletcher available following a series of injuries and picked the Sunderland player for the Warsaw trip despite the reservations of Black Cats boss Gus Poyet.
Fletcher made his comeback from a month out with an Achilles knock by coming on for the final half hour of Sunderland's Capital One Cup final defeat to Manchester City on Sunday and McGhee is keen to involve the 26-year-old.
"We think he has potential to be a really key player in the campaign," McGhee said.
"What we want now is, aside from anything that happened at the weekend, we want him to step up to show that he is the man to lead the line, as we do with the others.
"We are just looking for a positive reaction from anybody who comes into the squad, regardless of the game they had last weekend or next week.
"They are here to play for the national team and that's hugely important."
Both Fletcher and Sunderland team-mate Phil Bardsley were excused from training but McGhee believes their trip to Warsaw can help them overcome their Wembley disappointment.
"Perhaps it's a great thing for them to get over it by being involved with the lads, being away from the club for a few days, and to go back and start an important part of their campaign to make sure they stay in the Premier League," he said.
Meanwhile McGhee claimed the captaincy had "not been discussed" after Darren Fletcher returned to the squad following a lengthy absence through illness.
Scott Brown has been wearing the armband in the Manchester United player's absence.
McGhee said: "We have never worked with him but we've only ever heard fantastic things about him as an individual.
"We know how good a player he is. We are absolutely delighted to have someone of his stature and quality back in the squad."