Former AFL great Terry Wallace has named St Kilda's Rowan Marshall and Adelaide's Reilly O'Brien as the two ruckman set to make major strides in in 2020.

Marshall enjoyed a breakout year for the Saints to establish himself as the club's no. 1 big man and arguably their most promising youngster, averaging 17.8 disposals and 28.4 hitouts per contest.

O'Brien emerged for the Crows to take over their first-choice ruckman mantle after Sam Jacobs was struck down by injury early in the season, averaging 15.3 disposals and 33.3 hitouts.

โ€œI went for the two improvers from this year to keep on improving,โ€ Wallace toldย SEN Drive last week.

โ€œThat wasย Reilly Oโ€™Brienย in Adelaide andย Rowan Marshallย for St Kilda.

โ€œMarshall is the one that really fascinates me in that Paddy Ryder comes into the mix.

โ€œDoes that help Marshall, does that hinder Rowan Marshall. Iโ€™m sure it will help his ruck work and the way that he goes about his trade because having Ryder, who is such a good ruckman and has been brilliant at the ruck trade over the years, is only going to assist him to get better.

โ€œRyder is going to take ruck time off him and does that freshen Marshall up to be better when he goes into the ruck, can he make it as a forward as well, itโ€™ll be interesting to see how that plays out.

โ€œThereโ€™s some (ruckmen) that need to be the main man.โ€

Wallace left the Western Bulldogs' Tim English out of the discussion, believing he needs another year of development.

โ€œI still think he might be another season or two away,โ€ he said.

โ€œIโ€™m saying quantum leap. I donโ€™t know whether it will come this year or whether it is still another 12 months away.

โ€œHe has got all the potential in the world.โ€