Her mother is a nurse and still resides in Gates Mills, and her father, William Davis, a well known author of "Wheat Belly", is a cardiologist working in Wisconsin.

[4] She made her debut on the ITF Junior Circuit in September 2008 at the age of 14, via wildcard at the 2008 US Open, losing to Ajla Tomljanović.

Davis was awarded a wildcard into the Australian Open, where she lost her first Grand Slam appearance against fifth-seeded Samantha Stosur in the first round.

[8] She officially turned professional in 2011 and won her first WTA Tour match in the Miami Open qualifying by beating Jill Craybas, in three sets.

While waiting to give a post-match interview in a corporate booth, she was knocked unconscious when lighting equipment fell on her head.

Davis made it through the qualifying rounds of the French Open, where she won her first major main-draw match against 30th seed Mona Barthel, in straight sets.

In February, she won the United States Tennis Association (USTA) Dow Classic title by defeating Alja Tomljanović in the final.

Her furthest advance for the remainder of the year was a quarterfinal appearance at the Bell Challenge in September, where she lost to Lucie Šafářová.

[19] At the Australian Open, Davis beat Julia Görges to advance to the third round of a Grand Slam tournament for the first time.

At the Wimbledon Championships, Davis upset Flavia Pennetta in straight sets and advanced to the third round of the tournament for the first time.

[22][23] Davis reached the semifinals of the Auckland Open, her greatest success in a WTA tournament at the time, before she lost to Venus Williams.

Playing on clay, one of her best surfaces,[3] she avenged her loss to Eugenie Bouchard at the previous year's Australian Open, defeating her in straight sets.

[28] Playing her first red clay-court tournament of the year, she easily advanced to the quarterfinals of the Morocco Open in Rabat, winning each of her victories in straight sets, before dropping a three-set match to Anastasia Pavlyuchenkova.

However, she lost in the first round of all four Grand Slam tournaments in 2017, including defeats to fellow Americans Varvara Lepchenko at Wimbledon and Sofia Kenin at the US Open, and by the end of the year her singles ranking had dropped to 48.

[3] To start the year, Davis was unable to defend her title at the Auckland Open after losing to compatriot Sachia Vickery in the first round.

[29][30] In May, Davis beat Ann Li to win the inaugural ITF FineMark Championship event at Bonita Springs.

[34] At Wimbledon, Davis lost in the final round of qualifying to Kristie Ahn, but entered the main draw as a lucky loser.

[35] Davis recovered from an injury break after losing the first set and ended the match with 45 winners to Kerber's 15, winning 12 of the last 15 games to claim her first top-10 victory since 2017 and only the fourth in her career.

[41] In August 2021, Davis entered the main draw at the US Open, where she defeated lucky loser Viktoriya Tomova in the first round in three sets, before losing to sixth seed Bianca Andreescu.

At the Indian Wells Open, she reached also the second round defeating Nuria Parrizas-Diaz, before retiring against 22nd seed compatriot Danielle Collins.

Davis began her season at the Auckland Open, where she defeated Tamara Zidanšek [42] before losing to Danka Kovinić in the second round.

84, qualifying for the main draw and recording wins over Sloane Stephens,[44] Ysaline Bonaventure,[45] Wang Xinyu[46] and Anna Blinkova[47] to reach her first WTA final since Auckland in 2017.

[citation needed] Davis reached the semifinals at the WTA 125 Dow Tennis Classic with wins over Alina Charaeva,[52] Varvara Lepchenko[53] and Whitney Osuigwe,[54] before losing to Alycia Parks.

[56][57] On offense, Davis hits deep ground strokes to move opponents backward, often setting up her backhand as a finishing shot.

[58][59] While playing on hardcourts, she will usually draw opponents forward and attempt cross-court winners, or send serves wide and hit backhands down the line.

"[62] During Davis's final junior year, Mary Joe Fernández commended her "speed, quickness, competitiveness and heart.

[3] Only main-draw results in WTA Tour, Grand Slam tournaments, Fed Cup/Billie Jean King Cup and Olympic Games are included in win–loss records.