4 of the top 10 players are featured here in Halle, including Daniil Medvedev (1), Stefanos Tsitsipas (2), Alexander Zverev (3) Andrey Rublev (4). Other big names appearing are Roger Federer (5) and most recent WImbledon Semi-Finalist Roberto Bautista-Agut (6).
Federer has already won 10 titles here in Halle, but is going for an 11th, as a warmup tournament before WImbledon in 2 weeks. It will be interesting to see how far Federer can go, and if he withdraws to save himself for the Grand Slam.
The Greek God might be a bit tired after a 5 setter against Novak Djokovic, so it is likely Stefanos will pull out here. Zverev has had some good runs on grass, but 4-5 years ago. Recent grass form has been a 1st round loss to Jiri Vesely. Similarly, Rublev lost in straight sets to Sam Querrey in the 2nd round in Wimbledon 2019. Federer is unknown if he can go the whole tournament, but it unlikely the 39yo can last. This leaves the draw very open, and could lead to a dark horse winning the tournament.
Roberto Bautista Agut (6)
The most recent performance has been a Semi-Final bout vs Novak Djokovic, who was the eventual winner. The Spaniard has a 68% win rate on grass, and holds some experience compared to other players in the tournament.
Daniil Medvedev (1)
Medvedev has a sharp serve, and should not be put out of position too much on the grass. Medvedev's positioning could well win him this tournament, but his mentality is often inconsistent. His biggest challenges will likely be Felix Auger-Aliassime and Sam Querrey in the road to the final, but would be clear favourites in both matches. If he keeps headstrong he should win the tournament.
Dark Horse:
Karen Khachanov
Karen Khachanov faces fellow compatriot Andrey Rublev (4), but usually does well against the country battle. Khachanov's serve is liked, and Rublev has only won 57% of his grass court matches in his career. Khachanov loves the aces, and should serve plenty on this surface. If he beats Rublev, he should have a relatively straight-forward draw until Medvedev in the final.