La Liga's heavyweights were both given a scare by third tier opponents in the Copa del Rey on Wednesday as Barcelona needed two late goals to beat Ibiza, and Real Madrid dug deep for victory over Unionistas de Salamanca.

Barca sit 44 places ahead of Ibiza and Madrid 56 above Unionistas but the lowly duo both came close to extraordinary upsets, only for Ibiza to lose 2-1 and Unionistas 3-1 in front of their jubilant home fans.

With Lionel Messi rested and not even on the bench, Antoine Griezmann proved the savior for Barcelona, scoring twice in the second half, including a 94th-minute winner, after Pep Caballe had given the hosts a fairy-tale lead at Can Misses.

Ibiza were at their visitors from the off, closing the gaps and snapping at their heels. If the home side's aim was to contain, they went one better by taking the lead in the ninth minute.

Twice Ibiza almost added a second as Angel Rodado scored after bundling through Clement Lenglet but too enthusiastically, with the goal chalked off. Then Rai Nascimento hit the post after being played in by Javi Lara.

Ibiza's pressing lost intensity in the second half and in the 72nd minute, Griezmann equalized. Frenkie de Jong's reverse pass was perfectly weighted, with Griezmann able to hit first time on the turn.

Ibiza looked set for an extra 30 minutes but Griezmann struck again. Jordi Alba slid him through down and his finish flew across German Parreno and found the far corner.

"Scoring gave them confidence," said Barca coach Quique Setien. "We were a bit sloppy, we gave the ball away and that gave them life. It wasn't easy."

For all the dominance of the ball, there was a lack of cutting edge against Ibiza, who restricted their star-studded opponents to one shot in the first half, Barca's lowest in any game they have played this season.

Griezmann's rescue act was cruel but important for Setien, who enjoyed a 1-0 victory in his first game in charge against Granada on Sunday but could hardly afford a loss of this magnitude so early in his tenure.

With a trip to Valencia to come in La Liga on Saturday, Setien left Messi, Sergio Busquets and Gerard Pique out of the squad. Youngsters Ansu Fati, Riqui Puig and Carles Perez all started.

Discomfort was more fleeting for Madrid, who conceded an equaliser in the second half following a brilliant run and finish from Unionistas' Alvaro Romero, only to restore their advantage five minutes later.

Juan Gongora turned the ball into his own net after Gareth Bale, back from injury and illness, scored his first goal for his club since September 1.

Bale's celebrations were notably muted and he had to go off in the second half.

"He sprained his ankle a little," said coach Zinedine Zidane. "I don't think it's much but tomorrow we'll see."

Bale announced his return to the Real Madrid line-up with a goal as his right-footed effort took an awkward deflection on its way in, even if there was little sign that he enjoyed it.

In the 57th minute, Romero, who was playing in the Spanish third tier last season, capitalized on a slip from Eder Militao to weave through and apply an excellent, lifted finish but parity was brief.

Gongora turned the ball into his own net under pressure from Brahim Diaz, who then added a third in injury-time.

Elsewhere, holders Valencia beat Logrones 1-0 while Segunda strugglers Tenerife knocked out La Liga's Real Valladolid with a surprise 2-1 win.

(With input from AFP)