The Briton, who has slipped to 16th in the world rankings during his time on the sidelines with a hip injury, linked up again with the eight-time Grand Slam champion in 2016, the duo having previously worked together between 2012 and 2014.
Murray will continue to work with Jamie Delgado and his physical team but has yet to disclose whether he will look to replace Lendl during the upcoming season. "We've had great success and learned a lot as a team", Murray said in a statement.
An injury-hit 2017 hindered their chances of further success, though, with Murray ending his season with three months to run because of a hip problem.
He has been a permanent fixture on Murray's coaching team since a year ago - with Lendl on a more part-time basis - and he will likely be the man in Murray's corner when the new season begins. He came back on board previous year just as his old client was running into form, and oversaw an extraordinary period in which Murray won 52 out of 55 matches before the end of the season.
Lendl said: "I wish Andy well going forward".
Murray will continue to build his fitness with a training block in Miami before heading to Australia in December ahead of Brisbane and the Australian Open.
"Andy will just be concentrating on getting healthy", former British number one Greg Rusedski told Sky Sports News. The battle is to be healthy for 2018.
In the singles, David Goffin set up a semi-final meeting with Roger Federer after the eighth seed secured second place in his group with a 6-4 6-1 win over fourth seed Dominic Thiem. "I think they have parted on very good terms".
Wisconsin tops MI 24-10
The Badgers (10-0) enter Saturday undefeated and will look to keep their College Football Playoff hopes alive. He stayed down for a couple minutes before sitting up on the field for a couple more minutes.