Dominic Thiem saw the semi-final against Diego Schwartzman slip from his grasp as the home favourite reached the Argentina Open final.
Kei Nishikori was unable to deny Stan Wawrinka in the Rotterdam Open semi-finals and the Swiss will go in search of ATP title number 17.
Former world number one Simona Halep was unable to close out the win from a set and a break up against Elise Mertens.
Dominic Thiem remained unbeaten at the Argentina Open, defeating Pablo Cuevas to reach the semi-finals.
Stan Wawrinka beat teenager Denis Shapovalov to reach the last four in Rotterdam, where he will take on top seed Kei Nishikori.
Elise Mertens will play in her first WTA Premier final this weekend after claiming the scalp of three-time major champion Angelique Kerber.
Simona Halep won five games in a row in the deciding set of a thrilling contest with Elina Svitolina to reach her first final of the season.
Dominic Thiem is on track for a third Argentina Open title after moving into the last eight.
Daniil Medvedev and Jo-Wilfried Tsonga continued their winning runs and will now meet in Rotterdam after setting up a last-eight encounter.
Simona Halep will take on Elina Svitolina in the last four in Doha, while Angelique Kerber will be the favourite to get past Elise Mertens.
Naomi Osaka enjoyed a breakthrough 2018 alongside coach Sascha Bajin but the two have parted ways.
Cristiano Ronaldo has been an instant success in Serie A, and Giorgio Chiellini has compared him to Roger Federer and Usain Bolt.
Victory over Marton Fucsovics in the Sofia Open earned Daniil Medvedev his fourth ATP Tour title.
Victory over Pierre-Hugues Herbert in Montpellier on Sunday earned Jo-Wilfried Tsonga his 17th ATP Tour title.
Juan Ignacio Londero broke through for his first trophy as he outlasted countryman Guido Pella 3-6 7-5 6-1 in Cordoba on Sunday.
Caroline Wozniacki pulled out of the Qatar Open due to illness on a day in which she was due to face Karolina Muchova in the first round.
Having beaten Stan Wawrinka in the Rotterdam Open last year, Tallon Griekspoor added the scalp of world number 11 Karen Khachanov.
Simona Halep's victory over Karolina Pliskova helped Romania knock defending champions Czech Republic out of the Fed Cup.
There were contrasting fortunes for Bernard Tomic and Tennys Sandgren at the New York Open.