Thursday, 14 September 2017: Doubles specialist John Peers could be the the key player for Australia in this weekend's Davis Cup semi-final against Belgium.

He is the least-known player in Australia's Davis Cup team but doubles king John Peers is shaping as the key figure in this weekend's semi-final against Belgium.

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Peers, part of the world No.1 doubles team with Finland's Henri Kontinen, will play in the crucial second-day rubber on Saturday in Brussels.

It is a match that could potentially take Australia to a decider against France or Serbia on home soil in November in what would be a first appearance in a final since 2003.

Peers has claimed 13 ATP doubles titles since 2013, first enjoying success with Britain's Jamie Murray before linking up with Kontinen at the start of 2016 and winning this year's Australian Open in January.

Six of those tournament wins have come on clay, the surface the Belgium team have chosen for the tie at the Palais 12 complex starting on Friday (10pm AEST).

Despite his strong form on the world stage, Peers was overlooked by a succession of Davis Cup captains until Hewitt took over and gave him his debut against the USA last year.

"His knowledge of the doubles game is huge," Hewitt said.

"He has played against and beaten the best players and will be a key man for us."

Hewitt will announce the line-up of his team at the draw which will take place at the Town Hall of Brussels on Thursday (1930 AEST).

The South Australian is pondering using Thanasi Kokkinakis instead of Jordan Thompson in the singles matches given the strong form he showed at the French Open in May.

Thompson, who is unbeaten in three Davis Cup matches, would then partner Peers in the doubles with Nick Kyrgios and Kokkinakis playing in Friday and Sunday's singles encounters.