A successful staging of this year's Irish Open was expected to boost hopes of the Open returning to the venue for the first time since 1951, but R&A chief executive Peter Dawson played down the prospects of that happening.
Dawson warned it would take some time before a view would be taken on adding Portrush to the nine-course Open rota, adding that any decision could still be a no.
But former US Open champion McDowell believes he and fellow Northern Irish major winners Rory McIlroy and Darren Clarke need not give up hope just yet of playing an Open on home soil.
"We know the current shortcomings of Royal Portrush, so I sort of expected Peter's answer, but they are minimal," McDowell said ahead of the first round of the 141st Open at Royal Lytham.
"I always keep saying to the guys that we are going to Merion next year for the US Open and that's going to be basically an all-seater tournament.
"There is not going to be much room around the golf course, so there are ways around it. So if they want to go back to Royal Portrush badly enough, they will go back there.
"There are a lot of factors involved and I have a huge amount of respect for Peter Dawson as he's a fantastic leader in golf. I know he will make the correct decision."
Dawson admitted the enthusiasm of the spectators was a strong point in Portrush's favour, but added: "If you were at the Irish Open and compare it with what we're doing here, we're talking 20,000 grandstand seats, and there I doubt they had 2,000 at the Irish Open.
"You're talking about a tented village here I would estimate 10 or more times the size it was at the Irish Open. And the crowd size at the Irish Open, whilst it was very good, was only as good as perhaps the lowest crowd we expect at an Open venue, ie Turnberry.
"A huge amount of money would need to be spent, in my estimation, to make Royal Portrush a sensible choice. That's not a criticism of Royal Portrush; it's a wonderful golf course, but the commercial aspects of it are quite onerous."
Northern Ireland amazingly produced three major champions in six events, with McIlroy succeeding McDowell as US Open champion and Clarke then winning last year's Open at Royal St George's.
Clarke and McDowell were among the early starters at Lytham , with Clarke out at 9:09am alongside Ernie Els and Zach Johnson, while McDowell teed off two groups later alongside Dustin Johnson and Hiroyuki Fujita.
England's Lee Westwood was sandwiched in between, alongside Masters champion Bubba Watson and Yoshinori Fujimoto, while Tiger Woods was in the group behind McDowell with Justin Rose and Sergio Garcia.
World number one Luke Donald was among the later starters with four-time major winner Phil Mickelson and former US Open champion Geoff Ogilvy.