German tennis star Alexander Zverev has said that he is "grateful" after facing no disciplinary action over allegations that he abused an ex-girlfriend.
The ATP opened an investigation into the world number 14 in October 2021 after he was accused of physical and emotional violence against former partner Olya Sharypova.
The governing body announced on Tuesday that a "lack of reliable evidence and eyewitness reports" meant that the allegations could not be substantiated, and Zverev escaped disciplinary action.
A 15-month investigation - where text messages, audio files and photos were assessed - was conducted, with primary focus on alleged incidents at the 2019 Shanghai Masters and events in Monaco, New York and Geneva.
Zverev denied the "baseless" claims throughout the investigation, and the 25-year-old has stressed that he is looking forward to putting the "long and difficult process" behind him.
"From the beginning, I have maintained my innocence and denied the baseless allegations made against me," Zverev posted on Instagram.
"I welcomed and fully cooperated with the ATP's investigation and am grateful for the organisation's time and attention in this matter.
"This decision marks a third neutral, third-party arbiter who has reviewed all relevant information and made a clear and informed decision on this matter in my favour.
"In addition to the ATP's independent investigation, I have also initiated court proceedings in Germany and Russia, both of which I have won.
"I am grateful that this is finally resolved and my priority now is recovering from injury and concentrating on what I love most in this world - tennis."
The ATP have affirmed that they will reevaluate the decision to take no further action against Zverev if new evidence comes to light, or if the German is found to have breached the governing body's rules.
ATP CEO Massimo Calvelli admitted that the allegations and investigation stressed the need for the governing body to be "more responsive" to such claims, saying: "The seriousness and complexity of these allegations required an extremely thorough investigative process and considerable resources.
"It also required us to turn to specialist investigators, which was new ground for ATP. We ultimately believe the exhaustive process was necessary to reach an informed judgement.
"It has also shown the need for us to be more responsive on safeguarding matters. It is the reason we've taken steps in that direction, with a lot of important work still ahead."
Zverev's 2022 season came to an abrupt end after he suffered a serious ankle injury in his French Open semi-final with Rafael Nadal, and he lost in the second round of the 2023 Australian Open to Michael Mmoh in four sets.