According to ESPN, Chelsea will play CSKA Moscow in a preseason friendly to help inaugurate the Russian team's new 30,000-seater stadium. While there's been no official confirmation from either side, the match would most likely be held the weekend before (August 6-7) the start of the 2016-17 Premier League season (August 13).
This will be the second third (thanks, commenters!) stadium-opening match for Chelsea in the preseason. The Blues will be the first ever opponents for Rapid Vienna in their brand new arena on July 16th and will be the first to play in the new Vikings stadium in Minneapolis, too. The match in Vienna will signal the start of yet another busy preseason, with training camp in Austria and a trip to the USA all squeezed into just one month of preparations for the season.
Players are due to report back on Monday, July 11th, but that date will be pushed out for those who might be involved in the latter stages of Euro 2016 (especially the final, which is set to take place the day before) or the football tournament at the Rio Olympics (which isn't even set to start until August 3!).
Chelsea's full pre-season schedule is shaping up as such:
Saturday, July 16, 17:00 BST: vs. Rapid Vienna in Wien, Austria
Wednesday, July 20, 20:00 BST: vs. RZ Pellets WAC in Klagenfurt, Austria
Wednesday, July 28, 11pm EDT: vs. Liverpool in Pasadena, CA, USA
Saturday, July 30, 3pm EDT: vs. Real Madrid in Ann Arbor, MI, USA
Wednesday, August 3, 9pm EDT: vs. AC Milan in Minneapolis, MN, USA
Weekend of August 6-7?: vs. CSKA Moscow in Moscow, Russia