The Blues can book their place in the Champions League knockout stages with a win, before travelling back to England to face Liverpool.
The fixture schedule will continue to pile up for Chelsea, who could play 21 games in 74 days if they beat Bournemouth in their EFL Cup quarter-final and successfully navigate their FA Cup third-round fixture.
"It's going to be a tough period now, not just this week," Alonso told the Evening Standard. "Everyone knows how the Christmas period is in England.
"We will have a game every three days between now and the start of February. We have to be well prepared and very focused, there are so many matches. We are getting kicks in games, we get tired, so recovery is very important.
If there is any point I don't feel I can help the team, I will tell the manager I'm tired. But I'm feeling good. I take the opportunity to rest when I can and work with the medical team to be 100% for each game."
Chelsea face a Liverpool side at the weekend that are yet to secure their last-16 place after losing a three-goal lead against Sevilla.