Athletic's domestic form has tailed off in recent weeks, with just one point from the last 12 available, and a trip to the Nou Camp to face Barcelona tomorrow [Saturday] has come at an unfortunate time for Marcelo Bielsa's men.
The fixture at the league's second-placed side arrives just 48 hours after Athletic's 4-2 win at Schalke in the first leg of their Europa League quarter-final tie.
The quick turnaround means fatigue is likely to be an issue, and Iraizoz has issued a rallying cry to his team-mates ahead of run-in that already boasts a Copa del Rey final against Barcelona on May 25 and the very real chance of a Europa League final on May 9.
"At this stage of the season everyone wants to win to achieve their goals, but now we have to buckle down and give it our all," Iraizoz told reporters.
"We have the extra motivation of knowing that we have played well until now, and that will give us the energy to continue forward because the effort needed will be maximum."
Goals from Fernando Llorente (two), Oscar De Marcos and Iker Muniain secured victory for Athletic in Germany last night, but the unfortunate scheduling means Bielsa will almost certainly be without Llorente and Ander Herrera against Barca as both are carrying injuries that prevent them playing twice in three days.
Any relegation fears have long since passed with the team 13 points clear of danger with nine matches remaining, so Bielsa may choose to make a number of other changes to keep his side fresh for the return leg against Schalke next Thursday.
Barcelona head into the match enjoying a red-hot run of domestic form having secured a seventh straight league win at Real Mallorca last weekend despite playing the last half-hour with only 10 men.
Thiago Alcantara's red card has since been rescinded so he is free to face Athletic, and he is likely to be involved as coach Pep Guardiola shuffles his pack ahead of the return leg of their Champions League quarter-final against AC Milan.
The first leg at the San Siro in midweek ended in a frustrating goalless stalemate, with Barca subsequently complaining to UEFA about the state of the Italian side's pitch, and the Catalans will hope for more joy in front of goal back on their own turf.
Defender Carles Puyol is likely to start at left-back as Adriano is still an injury doubt. If he does play, the Barca captain will overtake Miguel Barnardo Bianquetti in second place on the club's all-time appearance list.