The 20 year old custodian, the cousin of St Helens' youngster Kyle Eastmond, joined Mark Gleeson and Ben Black in penning a new deal earlier this week.
Greenwood has excelled over the second half of the year after a rocky start, fully vindicating coach Matt Calland's decision to lure his former Hopwood College protege to the club from Leigh.
Greenwood's performances have apparently not gone unnoticed by rival bosses either, but the Oldham junior was adamant that leaving was never an option.
"There was no doubt in my mind that I wanted to stay, it was just about getting the deal done as soon as possible," said Greenwood.
"That's what we did as soon as Matt came to me because I knew I wanted to be here next year.
"You get interest from other clubs, and you can take that as a compliment, but there was only one place I wanted to be.
"Now the deal's done and I am really happy.
"I am excited by the prospects of the club as a whole and I want to be part of that."
Greenwood admitted his early days at the club had been far from easy, with university commitments compromising his ability to prepare properly.
"People don't realise that it can take time to settle into a new club, new surroundings," said Greenwood.
"I was doing a lot of travelling early on, three hours a night from Liverpool for training.
"That takes it out of you, but I was keen to keep coming, keep trying and keep aiming to prove myself.
"But as the season went on I started to get into the swing of things and started enjoying it a bit more and the performances have come along with that.
"I want to improve next year and I want us to improve as a team too.
"I think there is a lot of improvement left in me: anyone who is 20 has a lot of potential they need to fulfil and if they don't think like that then they should quit the game now."

WHITEHAVEN prop Mark Jackson has been banned for two matches after a clash with Halifax back rower Richard Varkulis at the Recreation Ground three weeks ago.
Jackson was found guilty of using his forearm in a tackle.