Actually I believe as well that Atletico board is putting a bit of pressure on Simeone and I think it started last year when his team barely produced any magic or performance but it's not only him to blame as the board didn't make any great transfers but it feels like Simeone era with Atletico Madrid is approaching the final.
Normally coaches are always blamed when things are not going well with their team so I'm not surprised that the board is mounting pressure on Simeone, they've supported him for years and he didn't win any trophies for them so I won't blame them if they start losing trust in him, Simeone's squad is very okay so there's no excuse.