Exiles go into the encounter well-rested and recovered after a two-week break, but with their hopes of making the play-offs rapidly fading following four successive Premiership defeats.
Not only that, but with just five games remaining in the regular season, they face a battle to earn a Heineken Cup place for the 2012/13 campaign.
That battle begins again this Sunday when they host a Leicester side fresh off the back of lifting the LV= Cup.
Richard Cockerill's men also sit third in the Premiership, breathing down the neck of Saracens and leaders Harlequins.
Although they are not as well rested as Irish, they are sure to provide a stern test in front of a near-capacity crowd at the Madejski.
And for Ojo, who made his bow for the Irish first team over six years ago, the occasion could not get any bigger.
"It's definitely one of the biggest St Patrick's Day games I've played in," the winger told the Chronicle. "Coming from where we've been, where we want to go and the challenges we have ahead of us, it's a massive game.
"It's a great occasion for the fans and for the players too, it's the biggest match of the season for us and we'll put everything into it.
"We know that it's going to be a very tough game, Leicester are a very good side, but we've had some time off and recharged the batteries and I think that has done us good."
In contrast to Irish, Tigers have been in action both of the previous weekends, battling their way to a narrow 17-16 win over Bath and then beating Northampton Saints in the LV= Cup final.
But after lifting silverware, and with the likes of internationals Ben Youngs, Tom Croft and Manu Tuilagi set to return, Ojo does not believe the Tigers will be jaded for the St Patrick's Day clash.
"Leicester will be fired up after winning the cup, they haven't had a break, but they won a trophy and that spurs you on," he said.
"They're also on a decent winning run and playing some good rugby. But we are rested and are raring to go, we will be going all out to win."
The match on Sunday will be Brian Smith's first since returning to the club as director of rugby last week.
And Ojo, who worked with Smith at Irish before he left to join England, says he's had a positive impact on the team.
"It's been good to have Brian back, a few of the boys know him from before he left to go to England, and it's given the whole place a bit of a lift," he said.
"I think the break came at a good time for us, results weren't going our way, we were very close and only losing by small margins. But we needed to step back and go away to look at things, we are not far away."
When the teams met earlier in the season, Irish stormed back 17 points down to claim a share of the spoils in a 24-24 draw.
Ojo hopes that his team can go one better this time around and says there will not be any added pressure on them playing in front of such a large home crowd.
"We love playing in front of big crowds and showing what we can do," he said. "We did well up there to get a good result in the end and we'll be trying to get the win on Sunday."
Alex Corbisiero is set to be available for Irish again this Sunday after his impressive displays for England at the Six Nations.
The 23-year-old was one of the standout performers in the final match of the championships as England beat Ireland 30-9 at Twickenham.
And he is likely to be joined in the squad by England Under 20 stars Marland Yarde, David Sisi and Anthony Watson, who all featured in the U20's successful Six Nations campaign.
Also at Toby Booth's disposal will be Ofisa Treviranus, who has returned to training after three months back in his native Samoa on paternity leave.
Despite the break there are still doubts over players carrying knocks, including Bryn Evans and Shontayne Hape.