Greenwood, who missed out on playing for England last season through injury, will go from the British & Irish Lions tour of New Zealand to the relative obscurity of National League One with relegated Quins when the new season starts.
England head coach Andy Robinson admits that not playing his league rugby at the highest level in the Premiership could cause problems for Greenwood's international aspirations, but is prepared to give him his chance.
"On a long-term basis there could be problems but Will is a quality player. We will make the judgements on Will when it comes to selecting the team.
"If playing a league below is going to make it difficult for him playing for England then I will have that conversation with him but at the present we will look to how he is playing for Harlequins.
"I will be totally up front with him and if necessary we will have those discussions one on one but I don't envisage that being a problem at the moment. We all understand the situation," said Robinson.
Whatever the outcome, Greenwood has no regrets about his decision to pledge his immediate future to Harlequins, to help the London club try to bounce straight back.
The England centre is relishing the opportunity of playing outside Andrew Mehrtens, the outstanding former All Blacks fly-half, who signed for Quins despite their relegation.
Harlequins will also be guided by new director of coaching Dean Richards, the ex-England and Leicester number eight and former Tigers supremo.
Relegation will take Greenwood, who started out with Preston Grasshoppers, back to his northern roots, playing at some less glamorous places, but he is relishing the prospect.
"It will certainly be different but I played in Division Four North in the old days. A few of the lads who have gone straight into professional rugby won't have been to some of the Sedgley Parks and Otleys of the world but they are great rugby grounds to go to, tremendous club spirits and they are the sort of trips that I am genuinely looking forward to.
"I am excited about the season, most of the squad have stayed, there are a few new acquisitions and Andrew Mehrtens is obviously world class.
"Dean always prided himself at Leicester on creating a good team environment and that's something he is trying to do at Harlequins.
"We have a good bunch of boys who are keen to put a few wrongs right. Last season is done and dusted and we are looking forward to a good season where we will obviously be welcomed ferociously in certain parts of the country."
As a big-name World Cup winner, he could be a marked man but said: "If I am and it creates a bit of space for people like George Harder and Gavin Duffy to score some tries then I will take that. But, with Andrew Mehrtens pulling the strings, hopefully we will be able to play some good-quality rugby."
Greenwood is even philosophical about the risk he is taking with his international career.
"Only time will tell. We are preparing for Pertemps Bees on September 3 and I will see what happens after that.
"If you are playing well and performing people will come and watch you. I am pleased to make the initial squad of 45 that's been announced.
"I have always been proud to stick on an England shirt and I am still available if required," he added.