PHILADELPHIA — The Cubs were outclassed in their 13-7 loss Monday to the Phillies at Citizens Bank Park.

They failed to execute in all three phases of the game. The pitching was subpar, the offense was listless until the game was well out of reach and the defense wasn’t nearly sharp enough as the Phillies capitalized on every Cubs miscue.

The Phillies already led 4-2 in the fifth — on the strength of two home runs by former Cub Kyle Schwarber — before loading the bases on a walk and back-to-back singles. Brandon Marsh followed with a two-run double to make it 6-2, but the Phillies didn’t stop there. They kept applying pressure and extending the lead against Cubs starter Javier Assad.

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Alec Bohm knocked in a run with a sacrifice fly, Bryson Stott had an RBI single and J.T. Realmuto delivered another run-scoring single before Cubs manager Craig Counsell pulled the plug on Assad, who allowed career highs of nine runs and 11 hits in 4⅓ innings in his second start of the season.

‘‘I just don’t think he got his sinker going and didn’t execute with his fastball,’’ Counsell said afterward.

The Phillies routinely hit the ball hard, running up the score and stringing together productive at-bats. The game got so out of hand that both teams started subbing guys out in the seventh. The Phillies scored in six of the eight innings in which they batted.

The Cubs were still in the game, trailing only 4-2, when they squandered a prime scoring opportunity in the fifth. They had runners on first and second with one out and Ian Happ, who leads the team in homers with four, at the plate. Instead of keeping the line moving, however, Happ grounded into a double play to end the threat.

Phillies left-hander Cristopher Sanchez used his sinker and changeup to keep the Cubs’ hitters off-balance all night.

‘‘We gave ourselves some chances but weren’t ultimately able to come through with the big hit,’’ shortstop Dansby Swanson said.

The Phil