LUXEMBOURG -- Monica Puig, the Olympic champion from last year, advances to her first final of 2017, triumphing over Belgian No.5 seed Elise Mertens, 6-2, 7-5 in the semifinals of the BGL BNP Paribas Luxembourg Open on Friday.

The Puerto Rican started the week strong by shocking No.1 seed Angelique Kerber of Germany in the first round, and sees her run continue to the championship match after maneuvering past Mertens in a hard-hitting affair with a plethora of risky tennis by both players.

Puig’s opponent in the final will be Carina Witthoeft of Germany, who outlasted French qualifier Pauline Parmentier in the earlier semifinal, 7-6(2), 1-6, 6-3. Witthoeft was able to shake off a second-set blowout to beat Parmentier for the third straight time and advance to her first WTA singles final.

Puig had an easy time of it in the first set, as Mertens struggled with errors while Puig's patented high-risk game was paying huge dividends. The Puerto Rican broke Mertens in the Belgian's first service game, and was totally untroubled throughout the rest of the opener.

After holding at love for 5-2, Puig broke Mertens at love, with a clean forehand service return winner. It was a fitting end to a set that saw Puig serve at 76 percent, win 79 percent of those first serve points, and face only one break point, which she saved.

For a moment, it seemed that Puig would run away with the second set as well. The 2016 Olympic gold medallist held at love for 1-0 and reached triple break point in the next game, extending her run of consecutive points to 15, dating back to the last two games of the first set.

But Mertens found the range on her shots which has led her to her current ranking of No.38 in the world, and saved all three break points to hold for 1-1. The set then became extremely competitive, as the missiles from Puig which had been routinely finding the lines began to miss their targets more frequently.

Puig had to steel herself on serve in the latter stages of the set. She saved two break points at 3-3, and then saved four more at 4-4, one of those on a controversial shot where a forehand called in on the sideline was vehemently argued by Mertens, to no avail.

After all of these chances and exceptional play, Mertens still found herself down 5-6 in the set, having been unable to break Puig once in the match. It was here where a barrage of forehands from Puig finally broke Mertens down, setting up double match point.

Puig took the first match point when Mertens sank a backhand into the net, closing out an achingly tight second set to seal the match. Puig's 7-for-7 perfection when down break point, as well as winning 86 percent of points when she got in her first serve, were the keys to her straight-set win.

Earlier, in the first semifinal, a topsy-turvy first set saw 10 of 12 games go against the server. Witthoeft held in the first game of the match, and used this initial advantage to lead 4-2, but Parmentier pulled out her only service hold of the set to knot the opener at four games apiece.

The German double faulted down break point at 4-4 to allow Parmentier to serve for the set, but the qualifier dropped serve at love for 5-5. In the next game, Witthoeft once more double faulted down break point, but again, the French player did not take advantage.

The first set tiebreak was dominated by Witthoeft’s forehand and serve, and she raced to a 7-2 victory. Witthoeft won all five of her break points in a set which was decided by the slenderest of margins at the last minute.

Any momentum the World No.73 might have had after that triumph was erased when Parmentier raced through the second set. The Frenchwoman staved off three break points in the opening game, and then quickly took the set 6-1, courtesy of effective serving and gritty play when behind in games.

Both players tightened up their games in the decider. Brilliant forehands from Witthoeft gave her the initial lead in the final set, as she broke for 3-1. Given that Witthoeft had only held once in the previous two sets, though, Parmentier surely felt that this lead was attackable.

But, surprisingly, that was the only break of serve for either player in the third set as more solid forehands and dogged scrambling by Witthoeft repelled any chances Parmentier could have obtained. A final forehand winner at the end of a long rally gave Witthoeft the victory after two hours and 15 minutes.