But another of Valverde's subs, Denis Suarez, struck for the first time since January as the visitors battled back in the second half, before Paulinho grabbed the victor just as it looked like they would have to settle for a draw.
Japanese global Shibasaki took matters into his own hands as he opened the scoring for Getafe with a spectacular volley from the edge of the box in the 39th minute, 1-0.
Dembele, Barcelona's record signing, had started against Juventus in the club's 3-0 Champions League win on Tuesday.
Getafe were inches away from moving in front when a neat passing move ended with Shibasaki's cross from the left being put into the side netting by a stretching Molina only a yard out, with a vital deflection from Pique as the pass was making its way to the striker doing just enough to put him off.
"Before the game started we saw that the grass was long and dry", said the midfielder, who replaced Andres Iniesta at half time.
Messi thought that he had levelled the scores in first-half stoppage time with a sensational free kick, but Guaita made an outstanding save to ensure that the hosts would take a one-goal lead into the interval.
Barcelona completed the comeback vs. Getafe and remain flawless in La Liga courtesy of new-signing Paulinho's strike late on. He also brought a great save out of Getafe goalkeeper Vicente Guaita with a wicked free-kick, and nearly scored after Paulinho, seeing a shot deflect wide.
Halftime substitute Denis Suarez curled in the equaliser from inside the box after being set-up by Sergi Roberto in the 62nd minute, 1-1.
And Paulinho was happy to get off the mark for his new side.
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