Lock, who was ranked the best junior tennis player on the continent after winning the International junior Tennis Championships (ITJC) held in Botswana early last month – surrendered the pole position to South Africa’s Wayne Montgomery.
He also fell six places down the ladder on the world rankings to number 69.
Lock, who lost in the quarter finals of the Africa Junior Championships to eventual winner Montgomery garnered 333.75 points. Montgomery, who was ranked number two garnered 377.5 points to dislodge the Zimbabwean who is based in South Africa.
Lock, who is set to be part of the Zimbabwean team at the Davis Cup team has had a bad April month.
Apart from winning the IJTC championships in Botswana, Lock has struggled in his recent games having failed to go beyond the quarterfinal stages.
In the Johannesburg Challenge, the Zimbabwean could not go beyond the first round and he also lost in the quarter finals of the Africa Closed Junior Championships to eventual winner Montgomery.
He also found the going tough in the two editions of the Riaan Venter Junior ITF where he again failed to go beyond quarterfinal stage.
In the girls Under 18, Valeria Bhunu, at number 10 is the best ranked female Zimbabwean in the Under 14 age group while Pauline Chawafambira is sitting seven places down the ladder.
Bhunu garnered 147.5points with Chawafambira attaining 101.25 points.
Ons Jabeur of Tunisia is the number one tennis player with 691.25 points while Madagascar’s Razafimahatratra’s 510points see her sitting on position two. Another Tunisian Nour Abbes, with 357.5points is sitting on position three.
In the Under 14 age group former continental queen Nicole Dzenga rose from position seven to occupy second position to Sameh Sandra.
Dzenga posted 588.75points compared to Sameh’s 613.75points.
However, the biggest mover is Tanaka Chakanyuka who rose from position 45 to position 11 with 333.75 points. Tariro Dembo fell two places down the ladder to position 30