Ellis said, "It was an awesome performance against Australia. All the players put their bodies on the line and as a defensive display, it was out of this world.
"We put them under pressure and came up with some big plays - firstly when Luke Eves intercepted for the first try and secondly when we forced the second half charge down.
"The thing that stood out the most was the way which we stepped up the intensity, especially around the ruck where we knew their scrum half was a threat. Now, we have to do it all again against South Africa."
South Africa coach Eric Sauls is expecting another physically demanding encounter. He said, "We expect it will be a very close contest. It will be tough. They are very physical, especially from the lineouts. They've got big strong backline players, good wings and full back, so it will be very tough.
"The contest will basically be determined by two packs of big forwards. If you get quality possession you can start building momentum and get guys running angles but as soon as you struggle with first quality ball, it will be a long day for you."
With two defeats from three pool games, Ireland, Italy, Canada and Scotland go head to head tomorrow in a bid to finish in 9th place in the IRB Junior World Championship. Also at the Arms Park tonight (7pm KO), Ireland, who followed up their defeats at the hands of Argentina and New Zealand with a win against Tonga, take on the Italians who were somewhat disappointing in Pool D where defeats at the hands of Wales and France were followed up with a scrambled victory over Japan.
Ireland coach Eric Elwood, who has seen his side develop well over the past 10 days said; "Our second half performance against Tonga was fantastic. We had a chat at half-time and a few harsh words were said because we didn't turn up at all and we were second fiddle. We got some great scores in the second half though and played some good rugby."
Full back Andrea Pratichetti, one of the stand out players for Italy in the competition so far, said; "We are thrilled to get a victory in the pool. It was a big match for us because we have stayed together as a group despite losing our first two games. Thankfully we cut out the errors that cost us so badly in those first two games and this time we were able to finish off our hard work. That had not been the case against Wales and France."
Tickets are available on the gate priced £8 for Adults and £2 for Children.