-snip-
Correct. There's still a chance. Not long after you said that, the score changed to Barcelona's advantage...
Xavi's decision was right, Lewandowski was introduced by Xavi, so Lewandowski became the player who provided Yamal with an assist in scoring the goal so that Barcelona's current position is 1-0.
Lewandowski is an experienced player. As a senior compared to Marc Guiu and Yamal, Xavi seemed to already know that if he brought in Lewandowski to replace Marc Guiu there would be changes.
This 1-0 advantage will be maintained until the end of the match. It's possible that the final score will not be 1-0, but 2-0.
After struggling hard to score, in the end Lamine Yamal managed to maximize his chance in the 73rd minute. It was a beautiful goal with his left foot, but Mallorca are a dangerous team who might still be able to score in the rest of this match. 1-0 is not safe because the tension in the match is still high, even Barcelona is still trying to double its lead to secure victory.
If Barcelona manages to win this match, it means they are only 5 points away from Real Madrid. However, this is not important because Real Madrid can widen the points gap by winning the next match against Celta Vigo.