The careers of many legendary footballers have been effectively defined by World Cup years: Think Pele, Diego Maradona, Ronaldo or Zinedine Zidane.

Theo Walcott has not attained the status of the aforementioned quartet, but Everton's new signing is another whose career has worked in this manner. The exception is that the 28-year-old never actually played a minute at the World Cup, yet the key watersheds in his career have nevertheless been 2006, 2010, 2014 and, now, 2018.

2006-10

It goes without saying that Walcott's career has been viewed through the prism of Sven-Goran Eriksson's incredible decision to select him for England's 2006 World Cup squad. Walcott was just 17 and had yet to play a minute of Premier League football.

The selection inflated expectations to the extent that literal comparisons were made with Pele, who won the 1958 tournament at the same age. Walcott later admitted it was a bad move.

"I was thrown into the limelight straightaway, having not even played a Premier League game and suddenly you are surrounded by these top-quality players and you are thinking, 'Do I deserve to be here? Being around top players helps you learn, but it was too early in my career."

But 2006 was, nonetheless, an important year and one that ended with him as a top-flight and international player. Walcott joined Arsenal from Southampton in January and made his Premier League debut on the opening day of 2006-07, assisting Gilberto Silva for Arsenal's first-ever goal at the Emirates Stadium.

His next four years were largely disappointing, though Walcott was unfortunate that apparently key contributions were subsequently overshadowed.

His first Arsenal goal was a brilliant opener against Chelsea in the 2007 League Cup final but the Gunners lost 2-1, while his memorable assist for Emmanuel Adebayor in a 2008 Champions League tie at Anfield was followed by two quick Liverpool goals and, ultimately, defeat.

After an injury-hit 2009, his substitute appearance vs. Barcelona helped turned a 2-0 deficit into a 2-2 draw and led Leo Messi to say Walcott was: "One of the most dangerous players I've ever faced." But more disappointment was to follow.

Despite scoring a hat trick away to Croatia in qualifying, more World Cup disappointment would follow when Fabio Capello omitted Walcott from England's squad for South Africa for failing to follow tactical instructions.

"It was the second day and I made a run inside from my position out wide on the right," Walcott said in his autobiography. "Suddenly Mr. Capello started screaming at me at the top of his voice. Training stopped and everyone stared at their feet and looked embarrassed. 'Theo,' he was yelling. 'I will kill you if you come inside like that again!' Despite his outburst, I never quite knew what was required of me."

In truth, the instructions seem simple: Capello wanted to stretch the play but Walcott was seemingly unaccustomed at having to follow strict positional guidelines.

After 12 years with Arsenal, in which he scored 108 goals in 397 games, Theo Walcott has joined Everton. Photo by Tony McArdle/Everton FC via Getty Images

2010-14

Being left out gave Walcott a wake-up call and prompted four years of largely excellent play. He hit a hat trick in Arsenal's first home match of 2010-11 and eventually scored nine league goals, as many as in his previous three campaigns combined. He provided speed behind opponents from the right and was a target for Cesc Fabregas' through balls, which allowed Robin van Persie to drop deep.

The following season was another decent campaign and featured a combined 16 league goals and assists, including a double in a 5-2 victory over Tottenham in February, which marked a turning point in Arsenal's attempts to overhaul Spurs and clinch a Champions League place.

2012-13 was probably Walcott's best season, though indecision over a new contract overshadowed it somewhat until he signed in January 2013. With Van Persie gone, Arsenal needed goals and Walcott provided them with 21 in all competitions. He was the club's top scorer and achieved double figures for goals (14) and assists (10) in the league, a feat generally only achieved by truly exceptional players.

By 2013-14 Walcott seemed to finally be maturing into an all-round attacker. He scored twice at Manchester City in a rare outing from the left flank and also performed well in his favoured centre-forward position during a 2-0 FA Cup win over Tottenham.

Until, that is, Walcott tore his left anterior cruciate ligament. 2014 should have been his year, with a World Cup on the horizon and Arsenal ending their trophyless run by winning the FA Cup. Instead, he didn't start another match as he recovered from injury.

2014-18

Since then, Walcott has struggled to recapture his best form. Despite still boasting tremendous pace, he looked rusty upon his return and it took until the final day of 2014-15 for him to have a serious impact; his hat trick vs. West Brom clinched a start in the FA Cup final against Aston Villa and he opened the scoring with a fine goal, perhaps the most important of his career.

But Arsenal had other options: Alexis Sanchez was the main speedy threat in the final third, a similar player to Walcott in terms of shifting between a wide role and centre-forward. Danny Welbeck was another like-for-like case, while Alex Oxlade-Chamberlain often played on the right flank until his departure for Liverpool last summer.

Walcott managed 19 goals in all competitions last season but Arsene Wenger's switch to a 3-4-3 system left no obvious place for Walcott, who found himself on the periphery. He hasn't started a league game this season and a move felt inevitable, just as another World Cup year began. At this stage, though, Walcott seems unlikely to make Gareth Southgate's squad.

Players' time at a particular club are often judged by their impact at the beginning and end, with the middle part forgotten. For example, Gianfranco Zola was magnificent upon his arrival at Chelsea in 1996 and superb in his final season -- 2002-03 -- but spent a portion of the middle years contributing relatively little.

Similarly, Xabi Alonso was an instant hit at Liverpool in 2004 and excellent before being sold to Real Madrid in 2008, but Rafael Benitez wanted to replace him in the intervening period with Gareth Barry after Alonso endured a couple of poor campaigns.

Walcott is the opposite: From 2006-10 his development was disappointing and, from 2014-18, he was rarely one of Arsenal's key performers. But, between 2010 and 2014, he was genuinely consistent and delivered a Premier League goal or assist every 117 minutes, which is an excellent rate.

Despite claims to the contrary, then, Walcott did fulfill his potential at Arsenal; it simply happened later than many anticipated and, seemingly, so long ago that many have since forgotten.