​Olwethu Makhanya (left) has been impressing on international duty for South Africa [Getty Images]Rangers defender Olwethu Makhanya continued his impressive start to the campaign by helping keep prolific Borussia Dortmund striker Serhou Guirassy quiet as South Africa defeated Guinea in Africa Cup of Nations qualifying.In just his second cap for his nation, the centre-back played the entirety of Saturday’s 2-1 victory, completing more passes than any other player and winning three of his four duels.The Guinean attack was led by Dortmund’s Guirassy, whose four goals in six games for his club this term contribute to a total of 64 in 102 appearances overall for the Bundesliga side.South Africa boss Pitso Mosimane hailed the display of Makhanya, who has arguably been Rangers’ standout summer signing, and praised how well he dealt with a top-level opponent.”Olwethu Makhanya was very good,” the head coach said. “He was up against a striker from Borussia Dortmund who is full of quality and he handled him very well.”The centre-back’s eye-catching form continues as new data from the CIES Football Observatory suggests his value is now at £12m, just a few months after Rangers paid £3m to sign him from Philadelphia Union.As Makhanya’s status soars, fans of the Ibrox club will be hoping his stellar level is maintained as Derek McInnes’ men aim to reel in wobbling league leaders Celtic.