Treadwell came of the bench against Fiji in the autumn series that year and then found himself in the international wildness.
Andy Farrell called Treadwell into this spring’s Six Nations squad and he won his fourth cap off the bench against Italy - also scoring his first international try in that game - and he retained his place in the matchday squad for the final test against Scotland, coming off the bench.
Treadwell feels a change in his playing style has helped him get back on the international stage.
“I try and get myself involved as much as I can, almost not watch the game, but be there in every single moment,” he said.
“For me it’s always been a case of playing well consistently rather than having a few good games and tailing off.
“It’s about the preparation during the week and making sure I’ve ticked all the boxes and am ready to go to put in the best performance I can.
“I took massive confidence from it, it was a nice surprise to be involved in the squad when it got announced,” Treadwell added.
“From there I thought, ‘I want to play, I’m here to play,’. I got the opportunity to play in two games, took massive confidence from that, and now I want to carry on learning and bring what I learnt in camp back here to Ulster.
“It was a surprise to get called back in. Obviously it’s something that you strive for. I got that taste in 2017 and was always really hungry to get back.
“It was unfinished business for me, again, I still want to keep on going and pursue that even more now.”
Treadwell enjoyed working with former Ireland captain Paul O’Connell, who is now part of Andy Farrell’s backroom staff.
“He’s obviously someone that I aspired to be like when I was younger and watching him, it was massive to pick his brains on stuff and being able to learn off him.
“It was massive, I really enjoyed it and took a lot from it.”
Treadwell is expecting another tough physical game as Ulster conclude their stay in South Africa with a clash against the Bulls.
“They’ve got electric backs, all the forwards are massive men, very powerful, our set-piece is one of our weapons and we’ll be trying to use that against their big packs,” he said.
“The Bulls are a good outfit and we’re looking forward to the challenge of it.
“It’s more about focusing on us. There’s a few things we left out there (against the Stormers) that were in our control and there were places where we thought we could have been better.
“We’ll try and rectify that this week and get those right against the Bulls.
“It’s always tough to go away from home but this year they have that calibre of player in their squad that does make it a bit more competitive and a bit more enjoyable for everyone.
“It’s a great competition to pit yourself against the best, to play against World Cup winners.
“It’s a massive test and experience that we have to walk towards and take in our stride.”