A much-changed Barca side lost at Real Sociedad nine days ago for their first league defeat in seven months. Guardiola could afford that, but it raised questions about their strength in depth.
Depth not Barcelona's strongest point
With three games left in Spain, 11 teams could still find themselves in two of the three relegation places. Almeria are doomed and down, but the scramble above them will run until the last day of the season.
Catalan sides Barcelona and Espanyol do not have such worries. Barca have a third consecutive league title in the bag in Pep Guardiola's third season as coach, while Espanyol were still pushing for a European place when the sides met in front of 90,000 at Camp Nou on Sunday night.
The players of both clubs - the majority of whom are home-grown and Catalan - get on fine and embrace each other with genuine affection after matches, while relations between the clubs at board level are much improved. The same cannot be said of the fans.
There were no Espanyol fans present at Camp Nou because of an argument over tickets, while Barca fans sang: "You are the budgies who fly straight into the stew" in reference to Espanyol's "Parakeets" nickname. That was when they were not singing "Campeones" (Champions).
Guardiola played a full-strength side which won 2-0. Barca will wrap up the league in the next week or two, but until they do, Guardiola has not been shy to tell people that, "We've won nothing yet."
He is right to be cautious. A much-changed Barca side lost at Real Sociedad nine days ago for their first league defeat in seven months. Guardiola played a weakened side in San Sebastian because he had the Champions League semi-final second leg against Real Madrid to consider.
He could afford the loss, more so after Real were also beaten at home by Zaragoza, but it raised questions about Barca's strength in depth.
Guardiola told journalists before the Arsenal game in March that Barca's B team was stocked with players similar to the talented Jack Wilshere. On a technical level that is correct, yet those players, and those who occupy Barca's bench, do not get as many games as those fringe players from Barca's Champions League final opponents Manchester United.
Unlike Guardiola, Sir Alex Ferguson enjoyed the luxury of playing a fringe side against Schalke in last week's semi-final second leg. Guardiola watched United triumph 4-1 at Old Trafford in person.
He will have learnt little from the much-changed line-up against the Germans apart from that United have more fringe players with more first-team games under their belts than his own side. Only 14 Barca players have started more than 10 league games, a core that seldom changes. The figure is 17 at Old Trafford, with Ferguson prone to change his team even more in cup competitions.
Barca's strongest starting XI is far more predictable than United's, though once his side do win the league, Guardiola is likely to repeat a tactic of previous seasons and drop key players to allow for recuperation and lessen risk of injury ahead of the Wembley showdown on May 28.
The only questions surround who will play in Barca's defence in London, specifically at left-back and alongside Gerard Pique at centre-half. The central role is looking more likely to be Javier Mascherano, the midfielder, with Carles Puyol or the fit again Eric Abidal at left-back.
The game has caught the imagination and 70,000 Barca members are expected to apply for the 18,000 tickets available to them for the Wembley clash.
Stung at being outclassed in Rome two years ago, United are watching Barca closely. Martin Ferguson, Sir Alex's brother who is the club's European scout, was at Camp Nou for the ninth time this season on Sunday. His advice is likely to form the cornerstone of United's tactics at Wembley Stadium.
And Barca's plan will be a push for continuity as they go for a third European Cup in six years.