After failing to beat Inter Milan in their two matches in the group stage, Barcelona must now face an inform and best-resourced Manchester United side in the Europa League play-off round.
"The draw has given us the most difficult tie, again," Xavi said. "Manchester United are a great rival, the worst that we could face.
"We will have to compete very well, they have improved a lot since the arrival of Ten Hag, they are fifth in the table."
In 2019, Barcelona beat United 4-0 on aggregate in the quarter-finals of the Champions league and the previous two times they played was in 2009 and 2011 when Xavi played against them in the finals, winning those matches 2-1 and 3-1 respectively.
Xavi added that having never won the Europa League title before, they were fully-focused on lifting it this year.
"You really like these terms, in the press. Failure, obligation," Xavi said.
"It's a challenge, the club has never won the Europa League and we're going to go for it," he added.