The 25-year-old Brazilian, signed for 160 million euros ($194 million) from Liverpool, had seen his debut delayed due to a thigh injury.
He replaced Andres Iniesta in the 68th minute and came on to a loud roar from the home crowd, with Barcelona leading 2-0 at the time as they looked to overturn a 1-0 defeat by Espanyol in the first leg.
Colombia centre-back Yerry Mina, signed from Brazilian side Palmeiras for 11.8 million euros ($14 million), was also on the bench.
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