Sarah Gregorius knows she is one of the lucky ones in getting to decide when to bring her football career to an end.

The veteran forward made her 100th appearance for the Football Ferns on Thursday (NZ time) and scored in the penalty shootout as they beat Belgium at the Algarve Cup in Portugal.

After the match she announced on social media that it had also been her last appearance for the team, as she was retiring to focus on her work with FIFPro, the global players' union.

Coach Tom Sermanni had given her the opportunity to reach the milestone, and to say goodbye to a team she's been a big part of – especially in the last two years, helping them rebuild after former coach Andreas Heraf's brief, but tumultuous time in charge – and she will be forever grateful.

READ MORE:

* Football Ferns win penalty shootout

* Gregorius set to be a Ferns centurion

* New Football Ferns star a real battler

* No Abby Erceg for Algarve Cup

"It's an unbelievable privilege and certainly not something that I expected or thought that I would have the opportunity to do," Gregorius said on Thursday.

"When you have the ability to choose to retire, you are already in a more privileged position than most athletes so I was very fortunate in that sense, and then I was fortunate that Tom is a people coach and he gets people and he understands the commitment that everyone has put in and he wanted to provide the opportunity to acknowledge that."

Gregorius entered the match in stoppage time, just after Belgium had scored the equaliser that eventually sent it to a shootout.

She was the second player to step up to the penalty mark for the Ferns, knowing her kick would be the final act of her career.

"As strange as it sounds, it's quite freeing, when you know you're retiring and you're well-prepared," Gregorius said,

"It really is the time when you say to yourself you can leave everything on the field – you're not thinking about the next game, you're not worrying about future selection. You have that competitive desire to win the game, but you don't have the next step in the back of your head as well.

"It was actually liberating. I felt very, very calm and very fortunate to be there, and I was just trying to soak it all in."

Gregorius sent her penalty into the back of the net and after five more of her team-mates did the same – and goalkeeper Erin Nayler made a crucial save – the Ferns came out on top.

Their next match is on Sunday (NZ time) against Italy, but Gregorius will already be back in Amsterdam by then.

"Tom and I spoke about this – I'm not exactly a wallflower and I'm a pretty big personality within the group," she said.

"They've brought me in as the 24th player so it's not like I'm taking anything away in a training sense by leaving the group and they need to start, sooner rather than later, adjusting to the environment without me in it,

"I've held a leadership role for a while and i'm excited to see who steps into that role now. The sooner they adjust the better off the team will be.

"For me it was always about trying to be as a small a distraction as possible, even though that's obviously not entirely going to be the case."

Gregorius had previously retired at the end of 2016 after the Rio Olympics, but returned at the start of 2018 and went on to finish with 34 goals from her 100 appearances, a return that puts her second only to Amber Hearn and her 54.

She played a key role in helping the team address complaints they had about Heraf's style of management later in 2018 – and in helping them rebuild once he departed and Sermanni took over.

Rio was her second Olympics, after London 2012, where she scored as the team notched a historic win over Cameroon and advanced to the knockout stage of a major tournament for the first time.

She also went to three World Cups – in 2011, where she scored in a loss to England, 2015, and 2019.

Gregorius said she had been hoping to continue through to this year's Tokyo Olympics when she moved to Amsterdam towards the end of 2019 to join FIFPro, but ultimately decided it wasn't possible.

"I was really committed to that when I first got there and FIFPro were very, very supportive, then I was training and trying to get settled into a new job and a new country, and by the time I got to China [with the Football Ferns last November] I realised it wasn't particularly sustainable.

"Knowing that I couldn't fully commit to the team and give it everything it deserves and give the shirt everything it deserves, it actually was a relatively easy decision. I knew that my spot could certainly be filled by someone who could apply that commitment and train and play at the level required, especially in an Olympic year.

"I wasn't really in a position to do the shirt justice and then Tom invited me to come in and get the 100-cap milestone and say goodbye to the group and to have a moment of reflection and celebration and I'm very, very grateful for that."