Ahead of his return to the F1 grid, Liam Lawson admits that he's facing a tough weekend in Austin.

The New Zealander replaces Daniel Ricciardo after RB called time on the Australian in Singapore.

Though test and reserve driver for RB and Red Bull, like most other test and reserves drivers Lawson has had little time in the current machinery other than 100 laps of Mugello in the RB20 recently tyre testing for Pirelli.

He was due to drive the current RB at Imola following the Belgian Grand Prix, part of what was claimed was a 'shootout' with Ricciardo, but with the Faenza-based outfit having opted to stick with the Australian, Lawson drove the 2022 AlphaTauri instead.

Having never driven the COTA track, Lawson admits that his return is going to be challenging.

"It's always a big jump," he told Newstalk ZB. "It's going to be tough to jump in Austin, I haven't done COTA before either, so even though I've done plenty of work, it's going to be a big challenge.

"But I would say I'm better prepared, definitely more prepared this year than I was last year," he adds, referring to Zandvoort where he was called upon to replace Ricciardo after the Australian crashed in the second practice session.

"At the same time, it's slightly later in the season this year, so these guys have done three quarters of a season, and there's nothing like...

"Obviously, I've been training like crazy all year to try and be ready for something like this, but even the few tests that I've done this year, it's, there's nothing like being race fit.

"It's going to be challenging in Austin," he admits.

Asked about the so-called shootout that never was, Lawson still believes he was being evaluated.

No, it was," he replies when asked about the Imola outing. "They were all evaluation days and they were designed to put lots of pressure on me.

"Basically, it was for an event like this where, to throw me in, a bit like last year, throw me in mid-season, they needed to know that obviously, I'd somewhat performed.

"They were definitely evaluation days."