Kevin Pietersen believes Friday's competitive comeback for Surrey represents the first real test of his fitness ahead of the Ashes.
Pietersen has not played for three months since being struck by a troublesome knee injury that wrecked his chances of playing in the Champions Trophy.
His primary focus has always been July 10 and the start of the Test series against Australia and he will line up at Headingley as his county take on Yorkshire in a four-day clash that should provide a thorough workout for the 32-year-old batsman.
If he comes through unscathed he will then make his England return in the second of a two-match Twenty20 series against New Zealand on Thursday.
Speaking to former England team-mate Darren Gough on talkSPORT, Pietersen said: "I'm just going up to Yorkshire to get through these four days.
"The professional in me will want to score as many runs as possible, but the most important thing is to wake up each morning and know there is no issue with my knee and to know I've turned a big corner and can handle a day in the field.
"That's the only thing that's not been tested. I can bat in the nets and I've done all the fielding drills you can do, but it's not the same as being in the field for 90 overs."
As for his unexpected appearance in England's Twenty20 squad, Pietersen sees the chance to make a swift return to the international stage prior to the glare of the Ashes as a worthwhile exercise.
None of England's other first-choice Test players will take part in the matches, with Eoin Morgan captaining in place of Stuart Broad and uncapped duo Gary Ballance and Boyd Rankin in an experimental group.
"It's great," said Pietersen of his inclusion.
"We did talk about it and we thought it would be good to get some international exposure, just get back into the international swing of things and to just get a lot of the nonsense out in the air - that I'm back playing blah, blah, blah.
"It's a perfect opportunity at The Oval and it'll just be nice to get back out there and whack a few balls, if I whack a few, and run around on the field, just get that buzz again. I'm very happy."
Speaking about the side, national selector Geoff Miller, said: "We have selected a squad with plenty of T20 experience as well as young players new to the international game.
"With an intense period of cricket coming up we are conscious that we need to manage the workloads of our players throughout the summer.
"This NatWest series gives an opportunity for players who have performed well in domestic cricket and on the England Performance Programme and with the Lions to step up and test themselves in an international environment.
"New Zealand are a talented limited overs side and with a World T20 competition less than a year away this series gives us a chance to look at a number of different options."
Ben Stokes has also been included in the squad, four months after being sent home from the Lions tour for disciplinary reasons.