Sevilla will host Celta in Week 22 of La Liga. Having previously failed to achieve full points at the time they traveled to Valencia.
In their last 5 meetings Sevilla won 3 times, lost 1 and ended in a draw. This is capital, at least for they have a better chance than Celta. Moreover, they will play at home, plus Sevilla have not tasted defeat in their last 7 matches in La Liga.
Another factor that will boost Sevilla's morale is that they are only 4 points away from the current La Liga leaders Real Madrid, if they can play with consistent wins, it is not impossible that they can become La Liga champions this season, there are still many games left and they will meet Real Madrid again.
Meanwhile Celta Vigo will play with little motivation, they are only in the middle of the table, safe from the relegation zone and difficult to move up to the top of the table.
When you are at a place where you know you are not going to European competitions next year but you are not relegating neither, like finish the year as 10th or something like that, then it becomes a bit of a challenge to motivate yourself for a win. After all there is no difference if you win or if you lose, it is going to be basically same result for you. Obviously you may end up with just a bit more money for finishing 9th versus 10th, but that's not really a big deal at all.
We have to remember that football clubs are a business as well and wins are what they provide to their customers who are the fans, but if your win means nothing then winning doesn't bring much to your customers. Sevilla on the other hand could win the league, probably won't but at least has that chance which I believe that could be a good motivation for them to win as many as possible.