Lehmann, who has been in charge of the side for only 17 days following the shock sacking of Mickey Arthur, watched his new charges bowl England out for 215 at Trent Bridge before reducing Australia to 75 for four to leave the match finely poised.
"It's even stevens," Lehmann told a news conference.
"Tomorrow is going to be a really big day and we are going to need to bat well."
Fast bowler Peter Siddle led the Australian attack with five wickets.
"We needed an experienced head and Peter gave us that," Lehmann said.
"The younger guys were a bit over-excited with the new ball but Peter stood up and did really well. I was really pleased for him."
Australia came into the series as huge underdogs after poor performances on the pitch and a series of off-field controversies but the appointment of the popular Lehmann as coach appears to have galvanised the team.
They looked likely to secure a first-innings lead before losing four early wickets as the England fast bowling attack struck back.
"We were really pleased to bowl them out for 215 but I thought they (England) bowled really with the new ball," Lehmann said.
"Conditions were favourable for swing bowling and England have some very good bowlers who were able to take advantage of that."
England fast bowler Steven Finn got the ball rolling for his side with the wickets of Shane Watson and Ed Cowan in successive balls.
"The overcast conditions helped, we'd have liked a few more runs after winning the toss," Finn said. "
But to have them four down was a good result at the end of the day."
James Anderson then produced a superb delivery, beating the outside edge of Australia captain Michael Clarke's bat to hit the top of the off-stump.
"It was an absolutely magic ball from Jimmy," Finn added. "
It's a tribute to how much work he does on developing his skills."
It was a dramatic day to start a run of 10 back-to-back Ashes tests and Lehmann was savouring the prospect of what is to come.
"Three hundred runs and 14 wickets that's not a bad day's cricket," he said.
"Hopefully, the English crowds saw today that we're here to play cricket and win back the Ashes."