Liverpool boss Jurgen Klopp rang the changes since the Reds got four games in less than two weeks.
The manager’s priority is the Europa League final, and he’s expected to field weakened teams in alternate games, the only exception would probably be the Chelsea game – since it’s a week before the final.
Odion Ighalo threatened after just eight minutes when he pounced on a loose ball from Lucas with a first-time shot from fully 45 yards that sailed narrowly over the bar.
Almen Abdi then watched an effort go wide from Kevin Stewart’s wayward header, while at the other end, Coutinho fashioned an opening for himself with some tricky footwork inside the area, but his final effort was deflected behind by Craig Cathcart.
Next, Alberto Moreno arrowed an effort over the bar and Abdi had a goal-bound shot superbly blocked by Martin Skrtel.
The breakthrough arrived with 35 minutes on the scoreboard – and it was a goal of great simplicity.
Coutinho collected a short free-kick just inside the Watford half and clipped a pass into the area, which Benteke knocked down into the path of Allen’s run. The Welshman beat Heurelho Gomes to the ball and steered it into the net.
The hosts began the second period with intent and within moments, Benteke teed up Coutinho with a low ball across the face of goal; however, the Brazilian was unable to make the necessary contact to turn it over the line.
Nevertheless, on 55 minutes Liverpool had Mignolet to thank for keep their advantage intact when he produced a wonderful one-handed save to thwart Ighalo after the striker had evaded two challenges on the edge of the area to open up an opportunity.
The Reds introduced Roberto Firmino for Coutinho on the hour and he almost made an instant impact, but his curler was straight into the gloves of Gomes.
Substitute Steven Berghuis then stung the palms of Mignolet with a fizzing hit from the corner of the box, but Liverpool made certain of the three points on 76 minutes.
Sheyi Ojo charged down Ikechi Anya’s attempted clearance and the ball ricocheted into the path of Firmino. He strode towards the edge of the area before striking goalwards. Gomes got his hands to the effort, but it squirmed beyond him and over the line.
As the contest ticked towards its conclusion, Benteke had an effort saved by Gomes and Ibe struck the outside of the post with the goal gaping, but the Reds had done enough to collect maximum points.
Liverpool remain in contention of qualifying for the Europa League next season, which would be their only route to Europe if they lose the final against Sevilla.