It was Matthews’ third Giro stage win and his first since 2015.
Pedersen finished second,ahead of Kaden Groves (Alpecin-Deceuninck) and Vincenzo Albanese (EOLO-Kometa) at the end of the 216-kilometre stage from Vasto to Melfi.
Corratec-Selle Italia riders Alexander Konychev and Veljko Stojnic were the early pace-setters,leading the stage for the first half of the race before being reeled in by the main group with 36 kilometres to go.
The drizzle,especially on the second half of the stage,caused several crashes but nothing that appeared too serious.
Pre-race favourite Remco Evenepoel (Soudal-Quick-Step) finished safely in the peloton and gained bonus seconds in the intermediate sprints – edging Primoz Roglic (Jumbo-Visma) – to extend his hold on the overall pink leader’s jersey to 32 seconds over João Almeida (UAE Team Emirates),who moved into second despite being involved in a crash.
Evenepoel has led the race since storming to victory in the opening time trial on Saturday.
Roglič,who is considered Evenepoel’s strongest challenger,moved up to third but was still 44 seconds behind the Belgian.