Lallana has not been able to recapture the form he showed for Southampton since his move to Anfield, though his club and country teammate Henderson believes the best is yet to come from the 26-year-old.
"Ads has been brilliant since he came to Liverpool," Henderson told FATV. "Obviously he picked up an injury which was unfortunate for him and also the team, but he's worked extremely hard behind the scenes to get back fit.
"Now I think he's looking back to where he wants to be, sharp, fit. You can see he's closing down, he's pressuring the ball when he's attacking.
"I think it's a massive plus for both Liverpool and England, because he's a fantastic player and he's still progressing as well, so hopefully he can just keep getting better."