This battle for number 1 should be interesting because as good as Kerber is, there are many that think that she does not deserve to be number 1. She is a great competitor, moves well, and has the knack to make most people feel awkward against her lefty strokes, but she doesn’t have a big weapon. While her forehand is good, it is not amazing and she does not possess as good of a serve as she could considering she is a lefty. Furthermore, her second serve is at times suspect and easily attackable. And last not but not least, it seems that everyone who plays inspired, aggressive, & consistent tennis will likely beat her or at least give her a very tough match. (Lost to Serena- Wimbledon, Lost to Puig-Olympics, Lost to Halep- Cincinnati, lost to Cibulkova- year end Championships, lost to Svitolina- Sydney, lost to Kasatkina- Brisbane). A number one should not struggle against so many people.
On the other hand, Kerber, might just hold on to number 1 spot mainly because Serena will probably not play so much this year. Serena’s interviews this year seem to indicate that she will be focusing on the grand slams. The other tournaments will be little more than warm-ups. But who can blame her, she is an elderly 35 years old, and she has a shot at pulling away from the 22 grand slam tie she now has with Steffi Graf. If she plays well at the slams in 2017 she could conceivably tie or even surpass the Margaret Court with 25 or 26 grand slam titles(if Serena wins 3 or 4 Slams this year.). Maybe this scenario isn't likely but don't count Serena out.
Serena Williams is still the best player on tour if she is playing well. Let's not forget that. She had knee and serve issues at both the Olympics and the US Open in 2016. Svitolina played very well to beat Serena at the Olympics, but Serena did not play well and at one point had 5 double faults in 1 game. Even her opponent Svitolina admitted, “Obviously, she was not playing well today.”
As for the US open Serena just didn't seem to have that same fight that her fans are used to seeing from her. An on form Pliskova took it to Serena in the semi-finals but Serena just couldn't get it together with either her footwork, her serve, or her confidence. Maybe this was due to the issues she was having with her knee. Whatever the case may be, she was not playing the type of Serena tennis she is known for.
So, in 2017 who will win the battle for number #1. I think it is Serena's hands. She didn't play so much tennis in 2016, only 8 tournaments including the Olympics so she doesn't have much to defend except her appearances in 3 slam finals and 1 slam semifinal. Playing relatively little tennis will give her a chance to keep her injuries to a minimum, stay mentally fresh and to possibly peak during the grand slams.
Kerber, is a good athlete, has improved her mental strength, and her consistency, but her serve and her return of serve are not good enough to give her an advantage at the beginning of the point. Big hitters and good servers will always have an opportunity to put her on her back foot. Furthermore, She struggles way too much against too many opponents. This will eat away at her confidence, wear her down physically, and not allow her to be fresh for the big tournaments.
Only time will tell. I wish both these ladies luck this year. They are both fighters and great for the game!!