But Gunnell, who won the gold in Barcelona in 1992, believes that she has what it takes to match her own feat in London.
Shakes-Drayton won a recent meeting at Crystal Palace two seconds ahead of reigning Olympic champion Melanie Walker with European champion Irina Davydova also trailing her.
And her time of 53.77 seconds, set in wind and rain, was the second-fastest time by a Briton behind Gunnell.
"This is a great opportunity for Perri. The field is really open. No one is running in the low 53s, which they usually are before a major championship," Gunnell told Eurosport.
"You have to take these opportunities. It's about mental strength: you have to know exactly how you are going to execute and what it takes to do so. You must have complete belief in your ability.
"That is what held me back in my first few years: running in a major championship is nerve-wracking. You know that this is maybe your only chance to change your life.
"Perri comes across as tough: I've told her in the past though that she shouldn't put herself down.
"She ran a great race in the conditions at Crystal Palace and she could get gold. She would have to run a particularly fast time to do so, though.
"Her face at the finish at Crystal Palace (pictured) said it all: she was shocked. That is a little boost for her and hopefully it has given her belief."
Gunnell, who has not talked to Shakes-Drayton recently, said she must run her own race.
"People worry too much about others sometimes if they have gone off too fast, but you just have to focus on yourself: what is my best touchdown time off the fifth hurdle, how it feels and so on," she said.
"But you cannot afford to get too technical with your approach. You have rehearsed it in your mind over and over and just have to give it your best shot.
"I haven't spoken to Perri or any of the other hurdlers in the last two months: the coaches prefer to deal with it themselves and stick with what they know, which is absolutely right."
Sally Gunnell was speaking at the official opening of the Mizuno Performance Centre - open to the public between the 24th July and 12th August at Centre Point Building, 101- 103 New Oxford Street. Visit www.mizunoseiei.com for further details.