For a young and talented player like Gavi, This kind of injury is a major setback. He injured the anterior cruciate ligament and the lateral meniscus of his right leg. This injury will require surgery and is expected to keep him out for several months. This doesnt only affect his ability but also affects his mentality.
The injury occurred during a training session and is the most serious injury that Gavi has ever suffered. it's not easy to recover from injury like this, especially for young players. he will need to rebuild his rhythm and instinct, and it will take time. Gavi's injury is also a major setback to Barcelona, who are already struggling with a number of injuries. Xavi Hernández will need to make some difficult decisions due to Gavi's absence, but I think he just need to wait for already injured players to comeback. He wont be able to afford to spend more money that can cause their future plan hard to execute with their current financial problem.
There are levels of injuries, some are easy to get back from and won't have any much effect on you while some are very much serious and will cause a lot of deprivations and backwardness in the player first before the team in general, Gavi's injury is one of those serious ones, he will definitely loose his skillfulness, stamina, ability to perform, he'll be out of the pitch for a number of months and that's enough to keep someone's mind on the drain, upon recovery, he definitely would require much time to get back to his right form.
For the team, the injury poses a danger in the teams performance worst of all when the player is a very crucial player for the team, the burden and task will be on the coach's shoulders to profer a working solution and replacement, and this is where the managerial skill comes in.
In cases when there are no good replacements, the team will be left with no choice than to endure losses as they'll keep coming. Injuries cannot be avoided, so one just has to be prepared for anytime it shows up, Xavi will work on Barcelona and find a second for Gavin while anticipating his return and him gaining his balance back.