Belgium became the first team to win a tie under the revamped Davis Cup Finals format, capturing both singles matches here Monday to secure victory over Colombia in Group D round-robin action.

They were joined in the winner's circle shortly afterward by Russia and Canada, who defeated Croatia and Italy, respectively, also on the strength of two singles triumphs.

Steve Darcis got the Belgians off to a fast start in Group D with a 6-3, 6-2 victory over Santiago Giraldo, in a contest that was a battle of ATP Tour veterans and former top-40 players who are currently ranked outside of the top 150.

The 35-year-old Darcis struck first when he broke his opponent's serve in the fourth game on Stadium 3 and never ceded the momentum the rest of the way.

Giraldo, who in 2014 became the highest-ranked men's singles player in his country's history, was unable to find the range with his flat-hitting shots from the baseline.

To the disappointment of several hundred Colombian fans at Madrid's Caja Magica complex, the 277th-ranked Giraldo repeatedly struck shots over the baseline when trying to attack and lost the first set without earning a single break point.

The Colombian got in trouble on serve once again in the third game of the second set, in which he battled back from a 15-40 deficit before dropping the game to fall behind 2-1.

The match then slipped away as the 158th-ranked Darcis, who has announced he will retire after the Australian Open in January, held serve at love and then broke once again to take a commanding 4-1 advantage.

He then wrapped up the victory three games later.

That win put the Belgians in a commanding position in the best-of-three tie, given that world No. 11 David Goffin was set to take the court against unheralded 23-year-old Daniel Galan, the world No. 194.

But the Colombian underdog announced his presence early on by breaking Goffin's serve twice to take a stunning 4-0 lead in the first set.

That was enough of a cushion for the Colombian in the opening set, which he won 6-3, but the Belgian former world No. 7 and ATP Finals runner-up in 2017 bounced back in the second set.

Leveraging his quickness and smooth-hitting baseline style, Goffin grabbed a key service break in the sixth game and knotted the contest at a set apiece a few games later.

Galan kept battling in the decider but his inability to convert a break-point opportunity in the fourth game proved costly as Goffin weathered his opponent's potent, whip-like forehand and elicited just enough unforced errors to wrap up a 3-6, 6-3, 6-3 victory in exactly two hours.

In round-robin action Monday in Group B, Russia topped Croatia thanks to singles victories by Andrey Rublev and Karen Khachanov.

Rublev took care of business in a straightforward 6-3, 6-3 victory on Centre Court over Borna Gojo, who was given the unenviable task of replacing injured 2014 US Open champion Marin Cilic.

Borna Coric, the world No. 28, then did all he could to knot the contest at one match apiece but eventually fell short by the score of 6-7 (4-7), 6-4, 6-4 to the 17th-ranked Khachanov, who recorded his first victory over the Croat in three attempts.

Russia is without world No. 5 Daniil Medvedev, who pulled out of the event due to exhaustion following his appearance in last week's ATP Finals, but showed their outstanding depth in recording the victory on Monday.

In Group F, Canada got a huge lift when 150th-ranked Vasek Pospisil stunned Italian world No. 12 Fabio Fognini in the opening rubber of that tie.

Pospisil, a former world No. 25, was called in as a replacement for injured 19-year-old rising star Felix Auger-Aliassime and rediscovered his best level at the right time in recording a 7-6 (7-5), 7-5 win on Stadium 2.

That was followed by the match of the day - a close battle pitting world No. 8 Matteo Berrettini against electric 20-year-old Denis Shapovalov, who has climbed to No. 15 with strong play in recent weeks under new coach Mikhail Youzhny.

Berrettini used his massive forehand to fight back from a set down but eventually succumbed 7-6 (7-5), 6-7 (3-7), 7-6 (7-5) in nearly three hours.

Even though the Belgium-Colombia, Russia-Croatia and Canada-Italy ties were decided in the singles, the doubles matches are still being played and the results of those contests could prove important later in the week when the eight quarterfinalists are determined. EFE-EPA