Jos Buttler says his first Championship century for Lancashire is an "important milestone" in his career.
The 23-year-old wicketkeeper, who hopes to force his way into England's Test team, struck 100 not out in a losing cause at Durham on Wednesday.
Buttler, who joined Lancashire from Somerset, told BBC Radio Lancashire: "Four-day cricket is something I'm really keen to improve on.
"And to get a hundred shows I'm making steps in the right direction."
Buttler impressed for England during the recent one-day series against Sri Lanka, including scoring the fastest ever one-day international century by an England player, leading for some to call for him to be named in the Test side against the same opposition.
However, captain Alastair Cook suggested Buttler was "not quite ready" to play Test cricket.
Matt Prior was restored to the team after being dropped for the final two Tests of the winter Ashes series in Australia and justified his selection with 86 in the first innings of the drawn first game at Lord's.
Buttler is now back playing at county level for Lancashire, for whom he has so far scored 382 runs in 10 Championship innings at an average of 42.44, including three half-centuries.
He continued: "I've become a better player over the past six to 12 months.
"I'm starting to work out my own game a bit, I've matured and become a bit more confident having played a little bit more international cricket. Hopefully I can continue that form and score more runs."
Buttler's unbeaten century almost took Lancashire to an unlikely victory over reigning county champions Durham, but they were eventually beaten by 27 runs, a defeat that left them second from bottom in Division One.