Chelsea boss Jose Mourinho said Eden Hazard's omission from his squad for the 3-0 win over Schalke was down to the player's timekeeping.
After making "11 mistakes" in the 2-0 loss to Newcastle on Saturday, Mourinho made six changes, including Hazard, for "missing a crucial training session".
"I don't want to lie. He's not injured. He forgot the time," Mourinho said.
"He's a kid, kids make mistakes and fathers have to be clever in the way they educate their sons."
Mourinho, who said his team showed a "good" response to the Newcastle defeat, added of his 22-year-old Belgian midfielder: "He's sad because he wanted to play.
"We won without him and Saturday he's back. End of story."
Samuel Eto'o scored twice and Demba Ba was also on target as Chelsea earned a win that gives them a three-point lead over Schalke at the top of Group E.
A point against Basle in their next game will secure their path to the last 16, but the German side could easily have been 2-0 up in the first six minutes and Chelsea were fortunate to go ahead after 31 minutes.
Schalke goalkeeper Timo Hildebrand was embarrassed when he allowed Eto'o to close him down and deflect his attempted clearance into the empty goal.
Eto'o grabbed another goal in the second half, after Chelsea keeper Petr Cech had produced a smart save to keep the Blues ahead, with Demba volleying in late on.
Mourinho said he was happy with the effort from his side, as David Luiz, Ashley Cole, Frank Lampard, Juan Mata, Hazard and the injured Fernando Torres sat out the match.
"After [the difficult start], we played very well and kept possession in a comfortable way and after the first goal we played well," the 51-year-old said.
"I know Petr Cech made a fantastic save for a possible 1-1 but everybody worked hard, especially the wingers against their full-backs.
"We have to understand why we win matches and not forget why we win. Today the players realised why we won this game, that is the most important thing."