Andre Villas-Boas praised Zenit St Petersburg for getting him off to a winning start with the Russian champions despite the turmoil of being dumped out of the Champions League.
Zenit beat Samara 2-1 on Monday to stay three points behind league leaders Lokomotiv Moscow.
"It was a really hard match," the 36-year-old Villas-Boas said after his first game in charge.
"We dominated the play in the early stages and deserved to score more goals in the first half. But after the 60th minute the team started to tire.
"The reasons were simple: the hard match at Dortmund, the intense practices after return to Saint Petersburg and of course the change of the head coach also influenced the players."
Zenit have had a traumatic week in which Italian coach Luciano Spalletti was sacked and the team went out of the Champions League 5-4 on aggregate to Borussia Dortmund.
"But I'm really pleased with my men performance. They acted well despite all the difficulties. I hope we will continue winning together," the Portuguese coach added.
Brazilian forward Hulk scored in each half and goalkeeper Yury Lodygin saved two penalties as Zenit bounced back from their Champions League exit.
"Luckily we have Yury. He really excited me with his performance and of course his penalty saves," said Villas-Boas.
"Our fans support helped us a lot especially in the second half when Zenit experienced difficulties," he said. "My first win here is the result of their passionate support as well."
The former Porto, Chelsea and Tottenham manager was appointed as Zenit's coach by the club owners, the Russian state-controlled gas giant Gazprom, who have invested heavily in the club.
His first aim is to overtake Lokomotiv and win a third straight title with the team that includes Hulk and Belgian star Axel Witsel who between them cost a reported 100 million euros.