Barcelona exacted revenge for their Spanish Super Cup defeat to Athletic Bilbao to get off to a winning start in La Liga thanks to Luis Suarez’s solitary second-half strike.
However, his strike partner ensured that miss didn’t prove costly as Suarez volleyed home early in the second-half to hand the champions all three points.
Luis Enrique’s men were returning to the ground where they were thrashed 4-0 in the first leg of the Super Cup just nine days ago and were without the suspended Gerard Pique, whilst Neymar wasn’t fit to take part after just returning to training following a bout of the mumps.
Athletic were also missing a number of first-team regulars, though, and struggled to match their high-energy performances in the two Super Cup matches after also playing in the Europa League on Thursday.
After a quiet start the game burst into life when referee Carlos del Cerro Grande controversially pointed to the spot when Suarez went down under a challenge from Gorka Elustondo.
However, Messi failed to open the scoring from the resulting spot-kick as Iraizoz flew to his right to make a brilliant save.
The Argentine has now missed five penalties for club and country in the past year and failed to find the net in 14 of the 63 penalties he has taken for Barca.
Iraizoz produced an even better stop moments later to prevent Suarez sweeping home Sergi Roberto’s cross to ensure Athletic went in level at the break.
The Uruguayan wasn’t to be denied just eight minutes into the second-half, though, as he connected sweetly on his left-foot with Jordi Alba’s cross.
Roberto was deputising in an unusual position at right-back after replacing the injured Dani Alves midway through the first-half, but his impressive showing continued as he smashed a shot off the bar from a narrow angle as Barca threatened to double their advantage.
However, the visitors suffered another injury blow when Sergio Busquets was stretchered off with an ankle problem and were left hanging on with a makeshift back four.
Ibai Gomez had the Basques’ best chance to equalise 10 minutes from time, but he blasted over when the ball fell invitingly inside the Barca box.
And Messi nearly sealed the three points with a stunning individual run past a host of tired Athletic defenders, reminiscent of his opening goal in the Copa del Rey final between the sides in May, but his finish lacked the accuracy needed to beat Iraizoz.