It means he performed horribly in the match. Dismal can mean depressing, but it also means lack of competence, effectiveness and skill. There's the expression I sometimes hear called "epic fail." The match was an epic fail for him.

(adjective) dismally: in a cheerless or dreadful manner You could also use: boring, gloomy, depressing

It means that he did not do good at all during his match. Dismally basically means sad or depressed. It can also mean not very lucky.