Kenya suffered a 1-0 defeat to Guinea on Thursday in the 2027 Africa Cup of Nations qualifiers.
Guinea bounced back from their 2-1 defeat to South Africa at the weekend to claim their first points in Group D, while Kenya remain without a win after two matches.
Guirassy, who were kept quiet against Bafana Bafana, made the difference in the 32nd minute. The Borussia Dortmund striker finished to put Guinea in front and give the hosts control of the match.
McCarthy turned to his substitutes after the break, bringing on Timothy Ouma and Ryan Ogam in an attempt to change the game.
Ogam had scored Kenya’s late equaliser in their 1-1 draw with Eritrea and almost produced another important moment when he went close 10 minutes into the second half.
The forward found space inside the area, but his close-range effort was denied by Guinea goalkeeper Mohamed Camara.
That proved to be Kenya’s best opportunity to get back into the match. Guinea defended their lead well during the closing stages to secure a clean sheet and their first qualifying victory.
Kenya, who have already qualified for the 2027 AFCON as co-hosts, now sit bottom of Group D with one point from two matches.
Read: Carlos Queiroz Steps Down as Ghana Coach Following Disappointing AFCON Qualifying Start
McCarthy’s side face a major test next month when they take on South Africa in a double-header.
South Africa lead Group D with six points, while Guinea have three. Eritrea and Kenya have one point each.