ZAGREB (AFP) - Croatia's Marin Cilic battled back from a mid-match collapse to beat Federico Delbonis of Argentina 6-3, 7-5, 3-6, 1-6, 6-2 in the opening rubber of the Davis Cup final in Zagreb on Friday (Nov 25).

Former US Open champion Cilic appeared to be cruising towards a routine victory at the Zagreb Arena only to lose his way after storming into a two-set lead over the world number 41.

Sixth-ranked Cilic, who made his second appearance at the ATP Tour Finals last week, secured the first two sets with a single break in each, but Delbonis claimed the third before racing through the fourth to force a decider.

Backed by an impassioned crowd Cilic regained his nerve in the final set, breaking his opponent in the first game and building on that momentum to eventually close out victory in three hours and 30 minutes.

Later, 2009 US Open champion and Olympic silver medallist Juan Martin del Potro takes on 37-year-old Ivo Karlovic in the second singles match.

Del Potro, 28, is a veteran of two losing finals - both against Spain in 2008 and 2011 - while Karlovic is the oldest player to feature in a Davis Cup singles match since 43-year-old Australian Norman Brookes in 1920.

Four-time runners-up Argentina are chasing a first title, while Croatia are looking to emulate their 2005 triumph over Slovakia.