Such is the nature of timing in football, a door can open as swiftly as it may slam shut.
Capitalising on any given situation can require a dramatic upturn in form. It can also need the cruel situation of an injury. For some, it will seemingly take the stars to align.
What most who find themselves on the outside all have in common is hope. Just ask Tom Bradshaw.
Raised in Tywyn, the striker had to bide his time before gaining his first Wales cap against Ukraine in 2016, just shy of three months before Chris Coleman's side embarked on a memorable run to the semi-finals of the European Championships in France.
Such was the forward's run of form for Walsall during the 2015/16 campaign, Bradshaw earned himself a place in Coleman's provisional squad for the showpiece event. However, the Shrewsbury-born frontman was rocked by the news that a calf injury sustained during a pre-tournament training camp in Portugal would rule him out of Euro 2016.
"That's one of my biggest gutters of my career," Bradshaw told WalesOnline. "Being out with the Welsh lads in Portugal in the warm-up camp before the Euros, to pull my calf out there, even when I felt it, you're kidding yourself when you say 'I'm sure it's nothing'.
"I had an MRI scan and it confirmed I would be out for four or five weeks. So I had to pull out of that and then, obviously, with what followed, how well they did to get to the semi-finals, it was just crazy. It was really bittersweet to watch but it was amazing how well they did.
"I went out to America on holiday but I made sure that every game that was on, I was at a coffee house or anywhere showing the game. It was brilliant to watch but I also had that element that I was just a little bit sick that I could have been there involved in that experience."
His 20-goal tally during that memorable campaign with Walsall had, through no fault of his own, ultimately counted for nothing when it came to wearing the red of Wales on the biggest stage. Such is the turbulent nature of international football, Bradshaw had to wait close to two years before earning his next Wales cap which came in Coleman's final game in charge against Panama.
Just three days after an experimental side was held to a 1-1 draw by the minnows at Cardiff City Stadium, Coleman left his post as national team boss to take up the managerial role at Sunderland, leaving Bradshaw and others in limbo.
A changing of the guard was inevitable following the appointment of Ryan Giggs as head coach after the failure to qualify for the World Cup in Russia, and 2018 represented a year of huge inconsistency with performances, squad selections and results.
Bradshaw, who began his career at Aberystwyth Town, was among those who travelled to China in March 2018, with his most recent cap coming in a 6-0 win over the locals in the China Cup competition. He was included in the squad for a 0-0 draw against Mexico in Pasadena but did not make it off the bench, and that was to be his last taste of international football. But that hope still burns brightly.
"I've had some amazing experiences with Wales. The day to day training of it all, it's just a great experience," admitted the 30-year-old.
"I had a great relationship with Chris Coleman. That was the bulk of my call-ups. Ryan Giggs came in. I had a couple of camps after that and then I don't know whether it was a loss of form or different personnel and I've struggled to get in since. But my relationships with both [Coleman and Giggs] were really good. They're memories I look back on really fondly.
"When it's involving your country, for me, I feel like you're picked on merit, it's not something you can question the manager on. There were times where I wasn't picked and I was gutted, but you've also got to respect that they have a vision in their head.
"It's something you desperately try to get in on by playing well for your club and scoring goals, but ultimately you've got to respect your manager's selection and just keep trying harder at your club to almost force their hand really. That's what goes through my mind when I'm playing and just trying to score as many goals as I can to impress again and hopefully get another chance on that stage."
Even the most hopeful of players appreciate the need for perspective, and while he certainly wouldn't turn down a place in Rob Page's 26-man World Cup squad, Bradshaw is realistic.
But with a Euro 2024 qualifying campaign just around the corner, the Millwall forward believes he could yet add value for his country in the future. He is currently the top scoring Welshman in the Championship having netted four goals so far this term, putting him ahead of young guns such as Swansea City's Ollie Cooper and Wigan Athletic's Nathan Broadhead who have three apiece.
The first of those came in a 2-1 win at Bristol City, and that effort at Ashton Gate was followed up with a first ever career league hat-trick that sunk Watford at The Den.
"It was a really special day," Bradshaw said of his stunning trio against Watford. "It was really up there for me with my debut for Shrewsbury way back in the day when I was 17 and scored twice, making my debut for Wales, coming on against Ukraine, and, obviously, the hat-trick. Those are probably my top three football moments.
"It's something any footballer just doesn't want to give up on. First and foremost you're trying to play well for your club, but you're hoping that, by playing well for your club, scoring goals and performing consistently, you really hope that it catches the eye of Rob Page and the international set-up. That's all you can do, that's all you're in control of and that's something I'm really pushing to do."
Whichever path Bradshaw follows over the coming years, he will always look back on his involvement in the national set-up fondly. Relationships with stars including Gareth Bale, Aaron Ramsey and Joe Allen were developed over a number of years while a connection was struck with the Red Wall who are now preparing to embark on a journey to Qatar.
"It's incredible. You haven't got to look back far to think these were pipe dreams," he said of Wales' World Cup qualification. "When the lads qualified for the Euros [2016], that was the first time, and now the same with the World Cup, the first time in 64 years.
"How far the team has come in a relatively short period of time, it really is incredible. I've got a lot of friends who are avid Wales fans and it's just a really proud fanbase. You see that passion in every game and the excitement of it all is brilliant for the country."
Time may not be on his side when it comes to a spot at what will be Wales' first World Cup appearance since 1958, but, for Bradshaw, hope remains strong that a door may yet be nudged open for him to wear the red jersey again before he hangs up his boots.
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