Pep Guardiola needed just four seasons to establish a legacy likely never to be matched, but even the 41-year-old could not withstand the immense pressure of coaching Barcelona anymore.

Guardiola revealed Friday he would leave Barcelona after the season, ending a four-year stint that already includes 13 trophies. He can secure a 14th title next month in his last match, the Copa del Rey final.

"Four years," Guardiola said, "is an eternity as Barca manager."

His demise, essentially, was a direct result of his own success.

With only one year of coaching experience for the Barcelona B team, Guardiola stepped up in the summer of 2008 to replace Frank Rijkaard, who just captured a Champions League title two years earlier.

Guardiola inherited a wealth of talent, but he also disposed of two-time FIFA World Player of the Year Ronaldinho, among others.

And in his first season in charge, Barcelona became the first Spanish team to win the treble, the Spanish league and cup titles, and the Champions League.

At the age of just 38, in only his first year in charge, Guardiola became the youngest manager to ever win the Champions League.

Attribute some of his success to his players as Argentine Lionel Messi, now a three-time world player of the year, was at the infancy of his brilliance and Spanish midfielders Xavi and Andres Iniesta, the brains behind both Euro 2008 and 2010 World Cup titles for Spain, were at their peaks.

Even though Guardiola raised the bar to an unmatchable level, Barca maintained a level of play during his entire tenure that deserves praise. European clubs such as Barcelona demand success, and Guardiola delivered.

The consequence, Guardiola aged well beyond his years during his short stint. The before and after do not resemble a fine wine, but instead a portrait like those of any President of the United States of America.

"It has been very demanding," Guardiola acknowledged, "and a coach has to be strong and be able to get that energy across to the players.

"I have to recover it and I'll do that by resting."

Guardiola admitted his decision was made in December, obviously a choice not made lightly by a man who right now defines Barcelona.

His playing career started with Barca in 1990, and he remained with the club through 2001, when like so many others, his end-of-career journey led him to clubs in Italy, Qatar and Mexico.

Guardiola, capped 39 times for Spain, came home in 2007. Although four seasons under the spotlight led him to leave home again, he departs the club after an unprecedented era.

Barca won the Champions League in 2009 and 2011 under Guardiola, and reached the semifinals in 2010 and 2012. The club won the last three La Liga titles, two FIFA Club World Cups, two European Super Cups, three Spanish Super Cups, and one Copa del Rey.

"I am leaving with the sensation of having done a good job," Guardiola said, "and I'm proud of what I've done here.

"Sooner or later I'll coach again," Guardiola added, "but I wouldn't be able to fill this emptiness if I were to carry on coaching now."

Good luck, Tito Vilanova, who will follow a similar path as Guardiola. As an assistant to Guardiola, Vilanova will step up to his first senior role. But, Guardiola leaves a void Vilanova, or any other coach, cannot possibly fill.

Barcelona has lost just 21 of 242 matches since Guardiola took over, and has made its claim as the best club ever. It is hard to attach the same label to Guardiola as the best coach ever, as his total body of work is incomplete.

But those four years? They, thanks to Pep, are unparalleled.