Defeat tonight would likely end the Reds' Champions League participation for the season and see them feature in the Europa League when European competition returns next year.
For that reason, the skipper knows any slip in concentration cannot be afforded.
But he insists Jürgen Klopp's squad are familiar with such high-stakes continental fixtures thanks to their Champions League qualifier against Hoffenheim earlier this season.
In his programme notes in 'This is Anfield', Henderson wrote: "Our situation is good, of course it is.
"We are top of the group, our destiny is in our own hands, we’re at home and we haven’t lost in the competition yet, despite facing really strong teams.
"But we also know if we lose tonight the most likely outcome is we won’t qualify. This gives this match a cup final feel to it and we have to have that mentality.
"We have to treat this game – players, staff and supporters – as the most important of the season.
"In some respects we’ve had this experience quite recently. Against Hoffenheim we came to Anfield with an expectation to finish the job.
"I’ve been remembering this week how we approached that second leg. We treated it like it was starting 0-0 and that an entire season’s work rested on us getting the job done.
"The atmosphere inside Anfield was electric and the players delivered. There was a healthy tension about it. Total respect for Hoffenheim and their abilities as a team.
"That attitude – in the dressing room, on the pitch and in the stands – is what we’ll all look to replicate against Spartak."
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