Scorers: AFC Wimbledon - Akinfenwa (36); Liverpool - Gerrard (12, 62)
Sean Rigg was not even reprimanded for the challenge and was soon causing problems at the other end, latching on to a flick forwards to hit a bobbling effort across the face of goal.
It was a missed chance Liverpool ruthlessly capitalised on, scoring with their first clear-cut chance of the match.
After neat team play, Gerrard played the ball out to the right and Manquillo’s cross was headed home by the Reds captain.
A Lazar Markovic cross-shot almost doubled Liverpool’s advantage but, while Liverpool were dominating possession, the Dons were growing into the tie.
Only a timely Martin Skrtel challenge prevented Matt Tubbs turning home a George Francomb cross, with Rigg’s fizzing strike from the resulting corner heading in until Mignolet impressively clawed over.
Akinfenwa – widely considered the strongest player in world football – was, unsurprisingly, proving a handful, with his presence seeing a James Shea goal kick through to Tubbs, who hooked an effort across the face of goal.
The 32-year-old was soon back at the heart of the action, heading wide before giving the home side a deserved leveller.
Francomb’s corner to the back post was bundled onto the crossbar by an under-pressure Mamadou Sakho, with Akinfenwa, whose bulk had hampered Mignolet’s attempt to catch the cross, stabbing home from close range.
Things almost got even better early in the second half, with a poor Gerrard pass allowing Sammy Moore a strike which deflected just wide.
That was a let-off for the Liverpool captain, who made amends from the resulting corner as he cleared Barrett’s header off the line, with Rigg firing wide as the visitors continued to wobble.
It was at this point, though, that the tide began to turn. Jordan Henderson saw a shot accidentally blocked by his own team-mate and Philippe Coutinho fired wide, before penalty appeals for handball against Barry Fuller were waved away.
However, the Wimbledon vice-captain could have no arguments with the free-kick award minutes later. Fuller was booked for his challenge on Coutinho and Gerrard made the home side pay, impressively curling the free-kick past Shea.
Dannie Bulman lashed one just over as Wimbledon attempted toequalise, while at the other end goalkeeper Shea impressively denied Rickie Lambert with his feet.
Coutinho was also denied by the Arsenal academy graduate, who then thwarted Markovic on the break after Adebayo Azeez effort was blocked. The Wimbledon substitute again threatened in stoppage time but there was to be no dream leveller as Mignolet smothered, with Gerrard seeing a hat-trick denied by a goal-line clearance.
Wimbledon: Shea, Fuller, Goodman, Barrett, Kennedy, Francomb (Sutherland 86), Moore (Pell 86), Bulman, Rigg (Azeez 79), Tubbs, Akinfenwa. Subs Not Used: Bennett, Oakley, McDonnell, Harrison.
Liverpool: Mignolet, Can, Skrtel, Sakho, Manquillo (Jose Enrique 71), Henderson, Lucas, Markovic (K Touré 86), Gerrard, Lambert (Balotelli 79), Coutinho. Subs Not Used: Moreno, Borini, Williams, Ward.
Referee: J Moss. Attendance: 4,784