First-half goals from Giannelli Imbula and Dimitri Payet set the tone at the Stade Velodrome as Marseille preserved their two-point lead atop the summit after eight rounds.
Jonathan Brison pulled a goal back for Saint-Etienne eight minutes into the second half and the visitors pressed for an equaliser late on but Bielsa said Marseille were always in control.
"With the exception of a few occasions in the second half, the team has not suffered too much," the Argentine said.
"I saw the effectiveness and maturity during the last 30 minutes.
"On a championship 38 days having played only eight days, we must think only to play well and not to analyse the rankings.
"I prefer to focus on the next game."
Marseille stormed out of the blocks in front of their home fans, Imbula opening the scoring in the seventh minute.
Payet doubled their lead in the 28th minute but Marseille began to tire after the break as Saint-Etienne reduced the deficit, leading to the introductions of Romain Alessandrini and Mario Lemina.
"During the first 15 minutes of the second period, there was an imbalance in fitness," said Bielsa.
"We corrected with the entry of Lemina and Alessandrini, they boosted the play of the team. Imbula had a very good first period and [Florian] Thauvin was destabilising in the one against one.
"I preferred to sacrifice these players to give more physical presence in the game."
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