Mercer enjoyed most of his tennis success while playing doubles. During his career, he made the finals in two doubles events. He achieved a career-high doubles ranking of World No. 112 in 1993.
Doubles runners-up (2)Edit
|Outcome||No.||Date||Tournament||Surface||Partner||Opponents in the final||Score in the final|
|Runner-up||1.||1992||Buzios, Brazil||Hard||Mark Keil|| Maurice Ruah
|6–7, 7–6, 4–6|
|Runner-up||2.||1993||Kitzbühel, Austria||Clay||Marius Barnard|| Juan Garat
|4–6, 6–3, 3–6|