He had only seen them make the semi-finals once before he became a senior international, but with the striker in their ranks they have reached the last-four stage three times.
An unlikely final against Brazil will take place on Sunday, and when you add in a first World Cup appearance since 1982 in Russia last year and the fact Guerrero is La Blanquirroja's all-time leading goalscorer it easy to understand how important he is to Peru.
Guerrero was plucked away from Alianza Lima by Bayern Munich in 2002 and won back-to-back Bundesliga and DFB-Pokals before heading to Hamburg in search of increased game time in 2006.
He struggled for goals in a less gifted team, though he got four during a run to the 2008-09 UEFA Cup semi-finals where HSV were denied a place in the showpiece by Werder Bremen.
Still, Guerrero's next move came as a surprise. At 28 and supposedly at the peak of his powers he swapped Hamburg for Corinthians in 2012, at the time coached by Brazil boss Tite. Within six months he was a Club World Cup champion, heading in the winner for an unexpected 1-0 triumph over Chelsea.
Guerrero had spearheaded Peru's run to the Copa America semi-finals a year prior and he did so again in 2015 - leading the scoring charts on both occasions - but his greatest achievement came in helping his country finish fifth in the mammoth CONMEBOL section of 2018 World Cup qualifying.
The delight of booking a play-off with New Zealand was short-lived, though, as Guerrero was ruled out of the matches due to a 30-day provisional suspension for failing a drugs test on October 5, 2017. He had tested positive for the cocaine metabolite benzoylecgonine, which he argued might have been accidentally ingested via a coca leaf in a traditional tea drink.
Without their talisman, Peru still claimed a 2-0 win on aggregate to earn a place in Russia, but regularly changing circumstances made it unclear whether Guerrero would be with the team.
An initial 12-month ban from FIFA was cut in half by its appeal committee to give him hope of playing, but the World Anti-Doping Agency (WADA) asked the Court of Arbitration for Sport (CAS) to look at that decision. Less than two weeks after the suspension ended, CAS extended it to 14 months to rule him out of playing in Russia.
However, an appeal to the Swiss Federal Tribunal (BGER) led to Guerrero's sanction being temporarily lifted while it considered the case, clearing him to lead his country at the World Cup.
The situation ended up resulting in him departing Flamengo for Internacional, who were dealt a blow when the BGER confirmed he would have to serve the remainder of his suspension.
Guerrero marked his long-awaited return to action on April 6 with a goal on his debut, heading home a corner in a 2-0 victory over Caxias in the Campeonato Gaucho.
The emotional 35-year-old said after the match: "I was very anxious. I was always apprehensive, uneasy. It was a difficult situation to accept what I have gone through, because of this unfair ban that I had.
"There were days that I was depressed, but I don't want to talk about it anymore. I just wanted to come back to training sessions, to my routine.
"To arrive early, play with my team-mates before and after sessions, to be together with my team-mates and experience the adrenaline of a game, all of this. I missed this very much and now I am here again."
Guerrero now has the opportunity to lead his nation to just a third Copa America title against hosts Brazil at the Maracana on Sunday.
He and Peru fought hard to get there and victory would be the crowning moment in the career of every player in Ricardo Gareca's squad.