The Durban outfit, fresh from a bye over the weekend, host another high-flying New Zealand team this week when the fifth-placed Highlanders come to town on Saturday.
The Sharks last played the Chiefs at Kings Park 10 days ago, with the match ending in disappointment as the home side were beaten 18-12.
Plumtree conceded the next five weeks would be a 'crunch period' for his side.
“We have a massive five games coming up before the June break, although our main focus right now is on the Highlanders,” the Sharks boss said.
“If we want to do something in this competition, we know that we have to be successful over all those games before the break."
Three of those matches are on home turf with this week’s match followed by the Force in Durban, a trip to the Cheetahs, the visit of the Stormers and an away game with the Lions.
Despite the Sharks losing five out of their nine games this season, the majority of losses came with bonus-points and Plumtree believes that will be crucial when the league phase of the competition reaches its closing stages.
“A lot of our games have been extremely close and the bonus points have helped us stay in touch with the teams around us,” he said.
"So we’re not far away, we’ve just got to keep boxing on, believing in each other and working hard. That’s going to be key.
“A lot of people out there will think I’m dreaming, but we believe in ourselves and we want to do well. If we can sort out some things internally, then we’ll be alright.”
Plumtree said his players all knew what was at stake in the coming weeks.
“We have to improve and there are certain things we need to get right for that to happen and that’s what we’re focusing on at the moment.
“Our preparation has to be more accurate – it’s little things like that – we’re hoping will make a difference starting with this week.”
There were also plenty of positives on the injury front for the Sharks with the biggest boost set to come in the front row where Tendai Mtawarira is likely to play his first game of Super Rugby this year.
The Springbok prop, who cracked a bone in his right ankle during February, played in back-to-back Vodacom Cup matches over the past two weeks, while fellow players set to return were Odwa Ndungane (groin) and Ryan Kankowski (finger).
“We’ve got a couple of guys back who could come in for consideration for selection which is good for us,” Plumtree added.
“A few played down in Cape Town for the Sharks XV, so our injury list is getting shorter and shorter and we have a few fit guys coming back into the group.”