Murray wasted two match points against Mario Ancic in Miami
Andy Murray has slipped out of the world's top 20 for the first time since August 2006 after his second-round defeat at the Sony Ericsson Open.
The British number one's loss to Mario Ancic in Miami means he drops nine places to 22nd in the world rankings.
However, the 20-year-old is ranked in eighth place in the ATP Race, which is based on his performances in 2008.
Murray has two ATP tournaments to his name this year, winning the Qatar Open and Open 13 in Marseille.
I'm happy with the way that it's gone, I just need to be a bit more consistent
"I missed the next four months last year because of injury so I haven't got any ranking points to defend and each week my ranking is going to move up for the next four months, so it doesn't really worry me too much," said Murray.
"It's been a bit inconsistent but I've won two tournaments and beaten Roger Federer so it's been a good start in patches.
"Some of the matches haven't been good, I've lost a lot of close matches. But I'm happy with the way that it's gone, I just need to be a bit more consistent."
The Scot will be back in action on 14 April for his first clay-court appearance of the season in Valencia.
Murray has enlisted the help of two-time French Open finalist Alex Corretja to improve his all-round game on the slower surface.
"I met him a couple of times last year, had lunch with him at one of the tournaments at the end of the year in Madrid and I thought he'd be a good guy to work with," Murray explained.
"Purely because I haven't played much on the clay lately and he's got a lot of experience and will teach me again how to do the things I used to do on the clay.
"It's the movement that's difficult, it's slippy under your feet, you slide into a lot of the shots and that's really different."
Spain's Rafael Nadal closed the gap on world number one Roger Federer after reaching the final in Miami, where he lost to Russia's Nikolay Davydenko.
Federer - who has yet to win a tour title this year - fell at the quarter-finals in Florida, losing out to Andy Roddick.
Australian Open champion Novak Djokovic maintained his place at the top of the Race rankings despite a shock first-round defeat to Kevin Anderson.