Line Calls, presented by FanDuel: Assessing the ATP Finals after two days of play

Day one: thrills and spills

The ATP Finals got off to a thrilling start on Sunday, with plenty of twists and turns in both singles matches.

Stefanos Tsitsipas started his campaign with a hard-fought three-set victory over Andrey Rublev, while Daniil Medvedev eased past Hubert Hurkacz in straight sets.

The day's action concluded with a marathon doubles match, which saw Nikola Mektic and Mate Pavic eventually prevail over Rajeev Ram and Joe Salisbury in a match tie-break.

Day two: more of the same

Monday's matches were just as entertaining, with Alexander Zverev and Casper Ruud both recording impressive victories.

Zverev defeated Matteo Berrettini in straight sets, while Ruud saw off Cameron Norrie in three sets.

There was another thrilling doubles match, with Kevin Krawietz and Andreas Mies defeating Pierre-Hugues Herbert and Nicolas Mahut in three sets.

What have we learned so far?

After two days of play, it is clear that this year's ATP Finals is wide open.

Tsitsipas, Medvedev, Zverev and Ruud have all shown good form, and it is tough to pick a favorite at this stage.

The doubles competition is also shaping up to be a close contest, with several teams showing good form.

What's next?

The ATP Finals continue on Tuesday, with Rublev taking on Hurkacz and Berrettini facing Norrie in the singles.

In the doubles, Mektic and Pavic will face Krawietz and Mies, while Ram and Salisbury will take on Herbert and Mahut.