Ospreys have won their last three encounters in the RaboDirect PRO12 since their 16-28 reversal at home to Glasgow on November 29.
The Welshmen have won their last two away games in the tournament but have not won three in a row on the road since May 2012.
After the trip to Ravenhill the Ospreys host Treviso and table-toppers Munster before travelling to Edinburgh and Tandy believes that run will determine if the 2012 RaboDirect PRO12 champions are equipped to lift the trophy again.
He said: "These next four weeks are massive for us in terms of how the rest of the season plays out, and beyond that, in regards to what we are trying to build here for the longer term, whatever the future holds for Ospreys Rugby.
"The focus is on Ulster this weekend then back-to-back games at the Liberty against Treviso and Munster. Some of the boys who have performed well over the last couple of games will get a chance to show what they can do while we have an experienced core to the group who will have to lead by example.
"Ravenhill is always a very difficult place to go and play, whatever time of the season you go there, but even more so during the international period.
"They have a strong core that is available to them throughout the season, with some world class overseas players, and that allows them to stay strong during this period.
"We know that it's going to be a challenge for us but we are up for it and looking forward to getting this period of games started."
The Ospreys are without 19 players due to injuries and international commitments while second row Perry Parker makes his first start and Jonathan Spratt captains the side from outside centre
For Ulster, Darren Cave gets the nod at inside centre with Jared Payne outside him while James McKinney deputises for Paddy Jackson at fly-half.
Iain Henderson and Luke Marshall have been released by Ireland and are named on the bench. Ireland Under-20s full-back Rory Scholes is also named as a replacement and is in line to make his RaboDirect PRO12 debut if called upon.
Ulster's only defeat in their last nine matches in all competitions came against Leinster at the RDS in the RaboDirect PRO12 on December 28.
They also came through the European Cup with a 100 per cent record to qualify as top seeds for the quarter-finals and their only defeat at Ravenhill in the last 12 months was 12-13 to Glasgow in round two.
Ulster have won three of their last four contests with the Ospreys, the exception being their 12-16 defeat at Ravenhill almost exactly 12 months ago.
This week, head coach Mark Anscombe extended his contract with Ulster until June 2015 and he admitted his work is far from finished yet.
"I have enjoyed my time at Ravenhill so far," he said. "We have made good progress, we have a great squad and some excellent young players coming through, so I am pleased to be committing for a further year.
"I said when I started at Ulster that I believed that this would be a three-year project. We are half way through that now. We have a home European Cup quarter-final and we are competing for a play-off place in the RaboDirect PRO12 once again.
"My focus over the next year and a half will be to finish the job that I have started and to bring some silverware back to Ravenhill."
At Ravenhill, 7.35pm. Live on BBC NI
Referee: Nigel Owens (WRU, 103rd competition game)
Assistant Referees: Dudley Phillips, John Carvill (both IRFU)
Citing Commissioner: John Cole (IRFU)
TMO: Marshall Kilgore (IRFU)
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