Lallana spent six years at Anfield before joining Brighton in 2020.
The Reds are only one point behind City in the title race, and Lallana hopes he can help his former club.
Speaking after their victory in London on Saturday, Lallana said: "We've done them [Arsenal and Tottenham] both a favour.
"We can't be biased. It's wide open.
"It's a great year in the Premier League. There's tough teams week-in, week-out.
"We are one of them [and have caused] upsets this year against big teams. Hopefully we can get one more on Wednesday night against City for my old team."