The Frenchman has produced a string of below-par displays at the pinpoint of United's attack in recent weeks, scoring just one goal in his last five appearances.
He is not the only Red Devils star underperforming right now, nevertheless, with the team as a whole failing to find the back of the net in each of their last three outings.
Murphy has offered his own theory as to why United are in dire straits, insisting Ole Gunnar Solskjaer’s problem lies with the fact Martial and fellow attackers Marcus Rashford and Daniel James all perform best on the left flank.
“Martial’s strength is when he gets the ball to feet he is good,” he told talkSPORT.
“His natural instinct is ‘give me the ball because I’m good with the ball’.
“So you’re asking him to play a role that doesn’t suit him.
“Manchester United’s biggest problem is that Martial, Rashford and James are all best off the left.
“James should be able to adapt to play on the right with his pace, but Martial is always better on the left and Rashford was having his best goal return from the left when he uses his pace to dribble and run at people.”
Solskjaer bolstered his attacking ranks at Old Trafford in the January transfer window, signing former Watford striker Odion Ighalo on loan until the end of the season while also completing a £67m deal for Bruno Fernandes.
Nevertheless, Murphy believes the Norwegian made a mistake back in the summer by offloading Romelu Lukaku to Inter Milan instead of selling Martial.
“This is why I’m surprised they gave Martial a five-year deal [last January],” he added.
“I would have been thinking of keeping Lukaku and maybe selling Martial.
“If you’re going to play Martial now you play him on the left, while Rashford is out. And you put the new fella in, because Ighalo is more of a no.9 – he’ll run behind and he’s good in the box.”
United’s woes continued on Saturday night, drawing blank once again in a 0-0 stalemate at home to Wolves.
Solskjaer bemoaned the injury and fitness problems he is currently facing afterwards, admitting his squad are “down to the bare bones”.
“We played so many games over the last two months - the players are down to the bare bones really, their energy levels are down and they need a break,” he told Sky Sports.
He later added in his post-match press conference: “I don't think it's confidence. We've just come off a 6-0 win in the cup, we've beaten Man City three days ago, it was energy.
“Wolves had 10 days to rest to prepare for this. We had two games, on a muddy pitch at Prenton Park, and the emotional energy at City.
“We dominated the game again, against them, 65 per cent possession, and we don't create too many big chances unfortunately, lacking a little bit of that spark, which is natural, we're on the end of a relentless run, 18 games in two months.
“Sometimes you get games that look a bit flat, but we still had 65 per cent possession, so it's not confidence, it's energy as well.
“So the break will be used to get the energy up, and also the weather is going to be nicer so we'll do more finishing, movement and patterns. We're looking forward to the last few months of the season.”