Pirlo scored after Gonzalo Rodríguez pulled down Fernando Llorente at the edge of the penalty area, earning a red card. Juventus hosts the final of Europe's second-tier competition on May 14.
Benfica, which lost to Chelsea in last year's final, advanced on 5-3 aggregate after a 2-2 tie against Tottenham. Nacer Chadli scored in the 78th and 79th minutes for Spurs, while host Benfica got goals from Ezequiel Garay in the 34th and Lima in the fifth minute of second-half stoppage time.
AZ Alkmaar and American forward Aron Johannsson advanced with a 0-0 tie at Russia's Anzhi Makhachkala and a 1-0 aggregate win. Basel, Lyon, Porto, Sevilla and Valencia also reached the final eight. The draw is scheduled for Friday.
Sevilla overturned a 2-0 deficit from the first leg against Real Betis, getting goals from Jose Antonio Reyes and Carlos Bacca in a 2-0 win that left the aggregate even, and it won 4-3 on penalty kicks. Sevilla's first spot kick by Vitolo was saved but Alfred N'Diaye and Nono failed to convert Betis' last two attempts.