Xavi proved to be the architect with all four assists as the La Liga champions produced a superb attacking performance to see off Jose Luis Mendilibar's side on Wednesday
Despite some notable absentees in the form of David Villa and Andres Iniesta, and with Lionel Messi initially confined to the bench with flu, Barcelona were in full control of the game after just 20 minutes courtesy of a finely-taken brace from Cesc Fabregas. However Messi still managed to have a considerable impact on the game by scoring the third and fourth goals for his side after coming on a substitute.
The away side set out to match their illustrious opponents by pushing men forward early on, and did manage to work the ball into a number of promising positions early on but failed to force Pinto into making any notable saves.
However after a heavy period of pressure, Barcelona eventually took the lead when Fabregas finished off a fine team move from inside the area after being played in by Xavi.
Xavi continued to dictate proceedings from midfield and he was the provider once more as Fabregas scored his and Barcelona's second just minutes later, the Spanish international lifting an exquisite chip over Asier Riesgo and into the top corner from 15 yards out.
As the home side threatened a repeat of Osasuna's last visit to Camp Nou, when they were comprehensively thrashed 8-0, Barcelona's players appeared to be lining up to get themselves on the scoresheet with Xavi, Thiago and Alves all coming close to adding to their lead before the break.
Messi was introduced around the hour mark as Pep Guardiola looked to take a comfortable lead to Osasuna's formidable Reyno de Navarra ground next week.
The Argentine came within inches of scoring Barcelona's third after miraculously dancing his way into the area and chipping the ball past both Riesgo in the Osasuna goal and his right-hand post.
It only took Messi 13 minutes to get on the scoresheet however, as he rose highest in a crowded penalty area to emphatically head home Xavi's cross midway through the second half.
The diminutive Argentine then completed the rout, making it 4-0 with a curling finish from the edge of the area after Xavi had again unlocked the Osasuna defence with a well-weighted through ball.
Barcelona travel to Osasuna on January 12 for the second leg of this tie, but, after their comfortable victory this evening they may already have one eye on a potential quarter-final clash against Jose Mourinho's Real Madrid who themselves take a 3-2 lead to Malaga ahead of their second leg.
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