England batsman Kevin Pietersen has admitted that his failure to score a Test ton in the last year-and-a-half has brought down his confidence level.
The 30-year-old South African-born right-handed batsman has not managed to reach three figures at Test level since March 2009.
Attributing the problem to his acrimonious removal as England captain in January 2009 in a row that saw Peter Moores sacked as coach, Pietersen said the problem was more psychological than technical.
"I'm not one of those guys who likes to say I'm playing well in the nets. Talk is cheap, but I'm trying so, so hard to break this barren run of hundreds," Pietersen told Sky Sports.
"It does concern me. I'm always looking to try and improve. I've got to look at the positives and drag my confidence up, which has been hammered in the last 18 months. I'm nowhere near the person I used to be but I've got to keep trying to work at it," he said.
"I've got a hell of a lot of starts and a hell of a lot of 80s and 90s. I was thinking if I'd converted those I'd have four hundreds in the Test year which is what I usually get.
"It's purely down to confidence and purely down to what's happened over the last 18 months. I'm trying so hard every day to get back to where I used to be. I'll get there," Pietersen added.
Pietersen has scored 5,306 runs, including 16 hundreds, in 65 Tests at an average of 48.23 in his career so far.