But once the 21-year-old had the support of the Swans' leadership group in his pursuit for more senior opportunities, he knew moving on was the right thing to do.
After considering a two-year contract with the Swans since the midway through the year, putting talks off until the end of the season and then meeting with Giants' coach Leon Cameron and list manager Stephen Silvagni, Lamb had plenty to think about.
He talked it through with his family when he went home to eastern Victoria after the season finished and considered the fact he believed he'd be more chance of playing seniors if he was wearing orange and charcoal.
Once he'd decided to leave – something he admitted he never thought would happen – he texted the Swans' 2013 leaders to tell them.
The response he got from Jarrad McVeigh, Kieren Jack, Adam Goodes, Ted Richards, Rhyce Shaw, Nick Smith, Jude Bolton, Ryan O'Keefe and Josh Kennedy validated his decision almost immediately.
"They just said we understand and you've got to look after yourself and there's more opportunity out there hopefully this year," Lamb told AFL.com.au this week, as the Giants prepared to play the Swans in the NAB Challenge in Canberra.
"They were pretty good and said if you need to chat let us know and we'll catch up for coffee.
"Once I told them I was moving it was a bit of weight off the shoulders.
"I was a bit nervous telling them at first because I thought they'd be a bit filthy but once I told them they were good about it and I just felt so much better.
"Then I was just excited to get to GWS and start pre-season."
Lamb was the only player to move in the NAB AFL Pre-season Draft after he delisted himself with the assurance that the Giants would pick him up on a three-year deal.
His relationship with the Swans has continued, despite having to move out of the club house he was living in with some younger players.
He relocated to Coogee where he lives with current Swan Tommy Walsh. Gary Rohan lives just up the street and he still sees Tim Membrey and Jake Lloyd a fair bit too.
In the end, the decision to leave came down the playing opportunities he believed the Giants could offer him.
"I just couldn't see myself fitting into the senior side at Sydney," he said.
"There were still five blokes from the previous year that had to come back from injury.
"I just thought it would be a bit hard and I was sick of being in and out. I just wanted to cement my foot and play regular senior footy."
"At first, I couldn't see myself leaving the Swans. That's probably one of the hardest things; leaving great leaders like 'Goodesy' and McVeigh. I was pretty close with all of them.
"But, once I sat down with Leon and Stephen Silvagni and they sort of gave a plan of where the club's heading and stuff like that, it was just an offer I couldn't knock back."
Lamb enters the season buoyed by the fact the Giants' players are confident they're in front of where they were 12 months ago, and Cameron believes their grasp of the game plan has steadily increased.
His pre-season at the club started slowly and then he was troubled by a niggle in his quad that halted things again.
But, after a few weeks of training strongly, Lamb is gearing up to face the Swans at StarTrack Oval on Thursday night in a match-up he's glad to face ahead of the round one clash between the crosstown rivals.
"I've been speaking to them through the week a fair bit and I'm looking forward to it," he said.
"We're coming out here to win and be competitive and it's just another game, but it's a bit more exciting because it's against my old mob.
"I'm just looking forward to getting it out of the way."
Twitter: @AFL_JenPhelan
