Valentin Barco, Mike Penders and Danny Welbeck were all handed starts after missing Monday's Premier League opener against Fulham, and each made a positive contribution.
Welbeck opened the scoring with a well-taken header from Malo Gusto's cross. Barco then played a key role in Chelsea's second goal, winning possession in midfield before finding Cole Palmer. The England international created the opening for Estevao Willian, whose effort led to an own goal from Hakeem Odoffin.
Penders had a quieter evening but kept a clean sheet on his competitive Chelsea debut.
Alonso was delighted with the performances, particularly Welbeck's contribution.
"For them it's a special day that they will remember," Alonso said.
"Mike will be happy because for a goalkeeper, to make his debut and keep a clean sheet feels good.
"Valentin had an impressive performance. Very dynamic, good with the ball, very aware of what was going on in the midfield.
"Danny was the patient player. He was the one who had to be in the box waiting for one good cross to come.
"Then he scored the first goal, which was important. A great cross from Malo and he did what he does best: to be in the right place and score."
Palmer was another standout figure as he completed the full 90 minutes and finished the game wearing the captain's armband after Reece James was substituted.
Alonso explained that Palmer's fitness allowed him to play the entire match.
"Cole has had a great pre-season and is well prepared, so he's one of the players who can take the 90 minutes," he said.
"We had an idea, depending on the context of the game, but Cole has a very good fitness level in terms of his stamina and now he needs to recover well on Sunday."
Chelsea now turn their attention back to the Premier League, with Brighton visiting Stamford Bridge on Sunday.
