The pair have been among a number of elite stars that have had time away from the court for numerous reasons since the summer.
Murray has been unable to play since his quarter-final defeat at Wimbledon in July due to a hip problem, while Williams gave birth to a baby girl in September.
Tiley, however, is confident that the Australian Open will welcome back some tennis heavyweights.
"All the top players will be back in Melbourne," BBC Sport quotes Tiley as saying. "I can tell you that in talking to Andy, he has been training and he is preparing for having a great year in 2018.
"[Williams] wants to come back in 2018 and defend her title. Obviously, at training now, there is several months to go and it will be up to her as far as where she is with her fitness."
The American pro won her 23rd Grand Slam title in Melbourne while she was eight weeks pregnant.