The Three Lions boss admitted that midfielder Sterling had asked to be rested ahead of their victory over Estonia on Sunday, which stoked a debate regarding how the Reds prepare their players.
However, Marsh has staunchly defended the club's approach to training.
The Reds first-team coach told The Mirror: "Our fitness programmes have been well documented.
"We try to recover the players as best we can to prepare for the game. We have a couple of days' recovery after the game and we work with the group of players for the next game.
"We know it's a tough fixture list with the amount of games and the quality of the opposition and the more players we have available, the better."
Liverpool return to action on Sunday with a trip to Queens Park Rangers.