The Southampton forward was included from the off in Friday's 3-0 victory over Peru at Wembley Stadium.
He lasted 73 minutes of that contest, earning his fourth senior cap before reports of a £25million bid for his services from Liverpool emerged.
Lallana's focus is very much on international matters at the moment, though, with the 26-year-old looking to convince coach Roy Hodgson that he is capable of leading the charge for global glory this summer.
He said after helping England to the welcome victory in their final fixture on home soil before focus shifts towards Brazil: "I'm good, really well. It was a good result and I am delighted with the team performance in the end.
"I was delighted (to start). Obviously, getting in the starting line-up for the first game in Manaus is what everyone's striving for and hopefully I've done enough to impress the manager and show him what I'm capable of.
"It was a good result and we move on to the next game."
Lallana believes England's preparations are shaping up nicely, as they prepare to head for Miami and two more friendly fixtures with Ecuador and Honduras, with training going well and no untimely injuries picked up.
He added: "It's been a great week, a hard week's training, a good bit of fitness, wearing layers to try and adapt for what we're coming in to.
"The weather's not been too kind to us this week, but the fitness of everyone is looking good.
"We haven't picked up any injuries, so that's the main thing. We'll recover and fly out to Miami on Sunday.
"It's a big week, we've got two big games out there in tough conditions, so we'll look to put in a couple of good performances like we did today.
"It's a strange feeling, you just want to take it all in, but it seems to be happening so quickly."