Dominic Thiem on Friday reached his first ATP Tour semi-final since May 2021 with a straight-sets victory over Peru's Juan Pablo Varillas in Gstaad.

The former US Open champion won 6-4, 6-3 and will next face second seed Matteo Berrettini as he looks to make a first final since the 2020 ATP Finals.

Thiem missed the second half of last year due to a wrist injury and lost his first six Tour matches this season.

"I failed to serve out at (5-2 in the first set), but it was also the nerves a little bit because it is my first semi-final in one and a half years," said Thiem, who also reached the quarter-finals in Bastad last week.

"I need the points to go back up the rankings. I was happy I was able to break the nerves."

Thiem, currently ranked 274th but now set to return to the top 200, will be hoping to win an 18th ATP title this weekend in the clay-court event.

"Tomorrow I can go into the match free, trying to do my best," the 28-year-old added. "When I travelled to Bastad last week I didn't expect to reach the quarter-finals there and then the semi-finals here.

"It is really, really good and I am happy with the progress."

Last year's Wimbledon runner-up Berrettini fought back from a set down to beat Spain's Pedro Martinez 3-6, 7-6 (7/5), 6-1.

The Italian missed Wimbledon following a positive Covid test last month, but is bidding for a third straight title after wins on grass at Queen's and in Stuttgart.

Berrettini was staring defeat in the face when trailing 5/1 in the second-set tie-break before reeling off six successive points and then easing through the decider.

"It is a crazy sport. At 1/5 I thought I was done. Then I played two good points and it was 3/5 and I thought 'Let's try'," he said.

French Open losing finalist and top seed Casper Ruud downed Spain's Jaume Munar 7-6 (7/3), 7-6 (7/4).

He will face another Spaniard, Albert Ramos Vinolas who needed three sets to defeat Chile's Nicolas Jarry 7-6 (7/4), 4-6, 7-6 (10/8).