The two sides meet in Sinsheim on Tuesday, before contesting the decisive return leg at Anfield on 23 August.
"We're at home first, and we have to try to win both games," Gnabry told kicker magazine after making his competitive debut for Hoffenheim in the DFB Cup first-round win over Rot-Weiß Erfurt on Saturday. "The two teams will approach it very differently [to their previous games], and will give absolutely everything. We've definitely got a chance. There's a lot on the line for both clubs."
With Champions League group stage football the prize, Gnabry is not exaggerating. Hoffenheim have never competed in European club competition, while Liverpool have played Champions League football only once in the last six seasons. For the player himself, the two-legged contest carries added significance following a trying spell in England with Arsenal.
"If you come up against a former club or, in my case, return to England, there's definitely a bit more excitement in the pot," said Stuttgart youth academy product Gnabry, who swapped Arsenal for Werder Bremen last summer. "Still, it's another game at the end of the day and we have to try to get the job done as a team."
Watch: Serge Gnabry's top five Bundesliga goals
A team player capable of moments of individual brilliance, Arsenal may already be ruing the day they let Gnabry go. The 22-year-old scored 11 Bundesliga goals for Bremen in 2016/17, his all-round talent earning a move to Bayern Munich in June. He won the UEFA U-21 European Championship with Germany later that month, before making it his "explicit wish" to join Hoffenheim on a season-long loan.
"I'm contracted to Bayern and know that's where my future lies, but I want to play as much as I can in the meantime," Gnabry said. "I was impressed by what Hoffenheim achieved last season. I'm here to help with that progression and further my own development."
Bad news indeed for five-time European Cup winners Liverpool.