The Royals are currently bottom of the Premier League but have yet to bring in big names despite the wealth of owner Anton Zingarevich.
Only Daniel Carrico from Sporting Lisbon and former Crawley midfielder Hope Akpan have arrived so far but McDermott has defended his signings, claiming they could go on to play big roles.
"The fans were probably critical when we signed Long and Doyle from Cork many years ago," said McDermott, quoted in the Daily Star.
"I think if the player's got qualities and can play in the Premier League, then whatever division they come from doesn't matter."
However, the 51-year-old manager admits more experience may be needed to help his side this season.
He added: "We're still looking for an experienced player and if we can find one who has played in the division that would be good for us."