Almost a year after her last match, Venus Williams will return to action in the singles category on Monday night. The seven-time Grand Slam champion received a wildcard entry into the Citi Open, a WTA 250 event to be played from August 1-7 in Washington DC.Her first opponent at this tournament is Canada's Rebecca Marino, who made her way to the main draw after winning two matches in qualifying. World No. 111 Marino has participated in all three Grand Slam events this year but failed to reach the second round in any.On Sunday, passersby at a tennis court in Washington found themselves in for a treat as they spotted Serena Williams joining Venus for practice before the start of the tournament. Fans who saw a video of the training session on social media expressed their jealousy towards those who witnessed the iconic sisters practice together live."I would literally have killed to watch this practice. Imagine the reaction of the fans when Serena just showed up!" a fan tweeted.Venus’ 125 mph serve@veeliever85024I would literally have killed to watch this practice Imagine the reaction of the fans when Serena just showed up! twitter.com/tennisoneapp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |16613Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hI would literally have killed to watch this practice 😂😭Imagine the reaction of the fans when Serena just showed up! twitter.com/tennisoneapp/s…"Wait - that’s Williams practicing? Omg I would rather see that than the tournament. Wow," another user wrote.lifelongtennisfan🏳️‍🌈🇺🇸@FkMeetings1@veeliever85024 Wait - that’s Williams practicing? Omg I would rather see that than the tournament. Wow2@veeliever85024 Wait - that’s Williams practicing? Omg I would rather see that than the tournament. Wow"Venus still cracking that ball and Serena still sliding (well, age is just a number really), totally impressive," another tweet read.Winnie Thomas @WinnieThomas11@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen Venus still cracking that ball and Serena still sliding (well, age is just a number really), totally impressive 🥰🥰61@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen Venus still cracking that ball and Serena still sliding (well, age is just a number really), totally impressive 🥰🥰Here are some of the other reactions:Brendan Churchill@BrenChurchillTwo sisters, Grand Slam champions, Olympic gold medal winners belting the ball around a court over the age of 40 and still on tour. You could have never... twitter.com/TennisONEApp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |761139Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hTwo sisters, Grand Slam champions, Olympic gold medal winners belting the ball around a court over the age of 40 and still on tour. You could have never... twitter.com/TennisONEApp/s…Kaiser@Celebitchy@KaiseratCBNot Vee making Serena run all over the dang court twitter.com/tennisoneapp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |322Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hNot Vee making Serena run all over the dang court 😭 twitter.com/tennisoneapp/s…Raenita@eeeducator@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen I am enjoying this camera angle. You really get to appreciate the athleticism of the players, and you get to learn from the players, too.52@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen I am enjoying this camera angle. You really get to appreciate the athleticism of the players, and you get to learn from the players, too.Tezzo3000@MauriceB__Imagine just casually walking in the park and you see Venus and Serena Practicing lol What a sight! twitter.com/tennisoneapp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |228Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hImagine just casually walking in the park and you see Venus and Serena Practicing lol What a sight! twitter.com/tennisoneapp/s…Winnie Thomas @WinnieThomas11@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen So much love, mad respect and admiration for these two!!!!5@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen So much love, mad respect and admiration for these two!!!!❤️❤️Donnelle 🛸@iAmNELLEZ_Venus running her all over that damn court. twitter.com/tennisoneapp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |295Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hVenus running her all over that damn court. 😂 twitter.com/tennisoneapp/s…Ajayi Monell@inspirEDucatorVenus and Serena practice is a sight to savor. Big sis is taking it to lil sis. twitter.com/tennisoneapp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |31Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hVenus and Serena practice is a sight to savor. Big sis is taking it to lil sis. twitter.com/tennisoneapp/s…Sanfrangirl22@sanfrangirl22@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen Lol. Where was @espn @TennisChannel . This would have been super cool for everyone watching at home :) this was a treat.1@TennisONEApp @serenawilliams @Venuseswilliams @CitiOpen Lol. Where was @espn @TennisChannel . This would have been super cool for everyone watching at home :) this was a treat.Quenchi@QueReduxSerena can still read Venus like a book. She took off for that drop-volley the second Venus made a move to hit it. twitter.com/TennisONEApp/s…TennisONE@TennisONEAppGoing all out for these #CitiOpen fans @serenawilliams | @Venuseswilliams | @CitiOpen |51Going all out for these #CitiOpen fans 🙌 🎾@serenawilliams | @Venuseswilliams | @CitiOpen | https://t.co/mpDPwmSL6hSerena can still read Venus like a book. She took off for that drop-volley the second Venus made a move to hit it. twitter.com/TennisONEApp/s…Venus Williams to play the Canadian Open as a wildcardVenus Williams will join Serena Williams in Toronto.Venus Williams received a wildcard in the singles category of both the Citi Open and the Canadian Open, with the latter scheduled to be played from August 8-14. Serena Williams will also play in Toronto after three years.The last time the 42-year-old Venus played a singles match was in August 2021 at the Chicago Open, where she lost to Hsieh Su-wei in the first round. The American made her tour comeback at the 2022 Wimbledon Championships last month where she partnered Jamie Murray to reach the second round in the mixed doubles category.Other players who will participate in the Citi Open this week include top seed Jessica Pegula, 2022 US Open winner Emma Raducanu, Simona Halep, Victoria Azarenka, and Elise Mertens.Serena, on the other hand, has decided to skip the WTA 250 tournament and will be seen at the Canadian Open before heading to Cincinnati for the Western & Southern Open, scheduled to be played from August 15-21 in Ohio.