Schneider has been on the comeback trail from the foot surgery he had at the end of last season, while Simpkin had a "niggle" about a month ago that interrupted his summer training.
St Kilda coach Scott Watters said Schneider had benefitted from a recent block of training, but there was no rush to push the 28-year-old on the eve of the season.
"We're really happy with his progress," Watters said on Friday as the Saints prepared to fly north for their clash with Greater Western Sydney at Blacktown the next day.
"He was pretty keen to let me know this week he was ready to go, but he's healthy, he's had a really good block of training and he's not too far away now."
Schneider didn't play seniors until round 11 last year after hamstring problems plagued him in the lead up to round one.
Watters said looking at the season as a whole was more important than focusing solely on a round one berth, with the former Sydney Swan expected to play around 70 minutes this weekend.
"I haven't even thought about where his selection sits the following week," the coach said.
"More importantly, after a really interrupted year, it's much bigger than just playing in round one for Adam.
"We want to make sure his preparation is really solid so he plays a whole year and we'll weigh that up next week."
Simpkin played 19 games last year in a season where he was one of the Saints' most improved players, and the 22-year-old is expected to play almost a full game in his bid to push for selection.
"It's tough for spots, which is what we like. Tom had a minor niggle four or five weeks ago that just interrupted what was a pretty good pre-season for him," Watters said.
"Again, he was just squeezed out of a list that is pretty healthy at the moment and he needs to earn his spot, and he'll do that - he's a good player."
Meanwhile, defender Sean Dempster is poised to miss between two and four weeks after tweaking his hamstring against Melbourne at Casey Fields last Saturday.
However, the Saints have been buoyed by his movement this week.
"It's disappointing to lose any player at any time," Watters said.
"Really pleasingly he had another run again this morning and we're really positive on his very early progression over the last week.
"He's really optimistic and ran really well this morning and we'll see where he sits in a week or two."
The Saints begin their premiership campaign against Gold Coast on March 30 at Metricon Stadium.
Adam Schneider is a forward in NAB AFL Fantasy. Heaveraged 67.5 points in 2012. Register your team at our AFL Fantasy Hub.
Jennifer Phelan is a reporter for AFL Media. Follow her on Twitter @AFL_JenPhelan.
