"He has felt really good in his standing starts so far this time," says Purdon.
"This week will be a different test as he started off 20m last time but he doesn't feel like he will gallop at the moment."
So should he win then?
"You respect horses at this level because they had to be good to get here but the way he won last start he should probably win again," says Purdon.
The reappearance of Krug adds great interest to the race but as good as he is, and he looked fit winning a between-races trial at Addington 10 days ago, it would be a remarkable feat for him to beat Self Assured if they both stepped away.
While Purdon is extremely confident with Self Assured he doesn't feel quite the same about Oscar Bonavena in the Flying Mile Trot, even though he couldn't be happier with his return last start.
"He was very good and he is coming up nicely," says Purdon.
"But I wouldn't say he was any better than the three other favourites (Majestic Man, Bolt For Brilliance and Muscle Mountain).
"They probably don't have a lot between them but with Majestic Man likely to go forward Oscar will probably be driven with a sit.
"He can win because he is very well but he is still coming back to it and I don't think he has proven that he is a horse who will just win a race like this without having some luck."
The trotter's mile could be a tactical affair, with Majestic Man likely to lead.