I'm a United fan but I know what you mean
I tend to be a "my second team's
wherever I happen to be living/working closest to at the time" fan.
Historically this has included various English teams and Valencia, Elche, Hercules (a blip due to working with a fan of theirs) plus some much much smaller clubs.
Valencia were awful until Christmas when they got a new manager. I won't say they're in good form, they're very inconsistent, but they're certainly capable of winning. However,
they play Sevilla in the Europa League on Thursday before the Sunday match. The Europa title is their only real chance of Europe and they will be throwing everything at that. I don't see the Chelsea games distracting Atletico as much as the Sevilla games will distract Valencia.