Novak Djokovic is concerned about Andy Murray slipping on the grass on his return at the Fever-Tree Championships but said the mental challenge will be his biggest to overcome.
Murray has not played since Wimbledon last year, but the three-time grand slam champion will make his long-awaited comeback against Nick Kyrgios in the first round at Queen's Club next week.
The Briton underwent hip surgery in January and Djokovic - who will also start his grass-court season at the same event - said it is not just a physical test the former world number one will face when he returns.
Djokovic, who has also been hampered by injuries, said: "He needs that support [from the Queen's crowd]. He needs people to back him up, to be behind him and show him that he was missed.
"I know how that feels. Having a couple of weeks at home, these are the events where he will give 100 per cent to try to get out on the court.
"He has been absent for longer than I have. I don't know how painful it is still, or not, for him to move around.
"But I think the biggest challenge will always be mental. In my situation that was the case. How to get it out of your head, understand that it's behind you, that you're fine now, that you're healthy and you can focus on your game rather than thinking 50 per cent of the time about whether or not something can happen.
"Does it hurt me? Does it not hurt me? Am I imagining things? Is it real? Is it not real? Then 50 per cent of the time you are thinking about your tactics and what you have to execute.
"If you don't have mental clarity on the court, especially on grass where everything happens very quickly, it's very difficult to play."
The Serbian added: "I don't know the state of his hips. But the one thing that could be a bit dangerous is slipping on the grass.
"That's something that is very unpredictable and grass is always this kind of surface where one wrong footing can make something go wrong, especially in the hips.
"I just hope for his sake that doesn't happen."
|Chelsea were too slow against West Ham - David Luiz|
|Tottenham star Kane acknowledges sub-par start|
|Rashid signs one-year all-format deal with Yorkshire|
|Brady and Patriots crash to back-to-back defeats|
|Gundogan looking forward to ´real test´ against Liverpool|
|Cubs move closer to clinching NL Central|
|Valverde bewildered by Lenglet red card as Barca boss questions VAR|
|Cronk a ´long shot´ to play in NRL Grand Final|
|Cleary re-signs with Panthers until 2024|
|Bills stun Vikings, Chiefs QB Mahomes impresses again|
|Tiger feels he can surpass Snead´s record after 80th victory|
|Ronaldo mentally stronger than others, says Allegri|
|MLS Review: Ibrahimovic scores as Galaxy end seven-game skid, Dallas reclaim top spot in west|
|Rose told Woods it was ´about time´ after win|
|Dustin Johnson regains number one ranking|
|Pogba: Sanchez will deliver at Man United|
|Federer, Zverev help Europe defend Laver Cup|
|I couldn´t sit or stand – Tiger Woods reflects on back woes after ending drought|
|Snead´s record in sight – Tiger Woods´ 80 PGA Tour wins|
|Nicklaus, Magic Johnson, McIlroy and Kane – Sports stars celebrate Tiger´s Tour win|
|Tiger Woods season in review: Tour Championship win caps remarkable comeback|
|49ers fear QB Garoppolo suffered torn ACL|
|World of golf is proud of Woods – Rose|
|WATCH: Tiger followed by incredible sea of fans at East Lake|
|Three takeaways from the 2017-18 PGA Tour season|
|Mbappe shows off signed Pele shirt|
|Tiger timeline: Woods´ fall and rise|
|Spieth´s breakthrough, Garcia´s Masters moment - Events between Tiger´s triumphs|
|Tiger Woods: I was close to tears on the last hole|
|Woods earns first win since 2013; Rose claims FedEx Cup|
|Pogba implores Manchester United to ´attack, attack, attack´|
|Valverde, Busquets and Vidal criticise Lenglet dismissal|
|Tiger Woods: The stunning statistics|
|Fitness hindering Dybala form, says Allegri|
|BREAKING NEWS: Woods claims first title since 2013, Rose wins FedEx Cup|
|Povetkin struggles leave Joshua with no Wilder fear|
|Guardiola targets Barca, Bayern dominance with Premier League priority|
|Centurions Rohit and Dhawan put India in final|
|Eagles top Colts as Wentz makes his return|
|Barcelona 2 Girona 2: Stuani brace punishes Lenglet red|
|Frosinone 0 Juventus 2: Ronaldo redeemed as champions extend perfect start|
|Gattuso: No alibis for two-faced AC Milan|
|Bangladesh hold on despite late Afghanistan charge|
|Composed Woods hits turn with five-shot lead|
|Chiefs´ Mahomes has another record-breaking Sunday|
|Saints QB Drew Brees passes Brett Favre for most career completions|
|Emery hints Leno may need patience after Cech display|
|Picamoles scores four as Montpellier batter 14-man Toulouse|
|Messi breaks LaLiga record|
|Worcester fend off prowling Tigers, Sarries go top|
|AC Milan 2 Atalanta 2: Last-gasp Rigoni rescues a point|
|Neymar keen to repay supporter affection|
|Pellegrini rues West Ham´s wastefulness|
|Paris Saint-Germain´s positive response buoys Tuchel|
|Lewis rekindles fond memories with Vilamoura triumph|
|Arsenal 2 Everton 0: Lacazette, Aubameyang extend winning streak|
|Stephens suffers as Osaka withdraws in Wuhan|
|Rhinos run riot to secure Super League status|
|Risk brings reward for victorious Marquez|
|Let´s have some fun - Wentz tweets message to Eagles fans ahead of return|
|Maybe in a year Chelsea will be at Liverpool´s level – Sarri|
|Under-pressure Rodgers bemoans ´bitty´ Celtic start|
|Slater should be banned for Grand Final - Fittler|
|Simon ends Bachinger fairytale to lift Metz title|
|Dominant Thiem reigns in St. Petersburg|
|Neymar hands young fan his shirt during Paris Saint-Germain victory|
|Quick-Step Floors storm to fourth time trial gold|
|Jorginho sets new passing record in West Ham draw|
|Rubiales slams ´crazy´ LaLiga schedule|
|Rennes 1 Paris Saint-Germain 3: Tuchel´s Ligue 1 record stays perfect|