The 22-year-old Mayo midfielder had been out of action since April 8 with a ‘rectus sheath’ injury but started against Claremorris and played for the entire 60 minutes.
Mayo manager James Horan was an interested spectator at the game and, presumably, if O’Shea suffers no adverse reaction, he is set to be back in Horan’s plans for the provincial final against Sligo on July 15.
However, despite O’Shea’s presence, and that of his brother Seamus (who was also returning from injury), Breaffy were no match for their South Mayo visitors.
Claremorris, who are managed by former Galway goalkeeper Martin McNamara, ran out 1-13 to 0-8 winners to book their place in the quarter-finals.
Elsewhere, defending champions Ballintubber also booked their place in the knockout stages yesterday as they maintained their 100% record.
Peter Ford’s charges, who are bidding for a historic third Moclair Cup success in-a-row, were never really troubled as they ran out 1-13 to 0-9 winners over Davitts in Clogher.
Last year’s Young Footballer of the Year, Cillian O’Connor, led by example up front and shot six points (five from frees) with his brother, Padraic, chipping in with 1-1.
With Mayo panellist Jason Gibbons in inspirational form at midfield, Ballintubber led 0-9 to 0-1 at half-time as Davitts, last year’s Mayo IFC champions, struggled to get going.
County star Alan Dillon tagged on a brace of scores for the home side as they streaked ahead by 12 points at one stage, and only a late string of consolation points from Davitts, including Michael Conroy (two) glossed the final scoreline a little.
Elsewhere, last year’s beaten finalists Castlebar Mitchels also clocked up their second win of the campaign with a 2-9 to 1-7 win away to Ballinrobe.
Goals from Ronan O’Boyle and Danny Kirby in the 30th and 31st minutes left the visitors ahead by 2-6 to 0-3 at the interval.
However, Ballinrobe came roaring back into contention after the restart with three points from Alan Murphy and a goal from Mayo minor James Quinn making things interesting. But with Mayo’s Barry Moran and Richie Feeney in fine form, Castlebar weathered the storm.
Meanwhile, the biggest shock of the day came in Tourmakeady as the locals ambushed Ballina Stephenites and emerged with a shock 0-10 to 0-9 win.
The hero of the hour was Tourmak’s experienced attacker Tom Naughton, who popped up to kick an incredible point five minutes in stoppage time to decide the issue.
The Gaeltacht side led 0-9 to 0-7 entering the closing stages but scores from Ger Brady and Seán Regan looked set to earn Ballina a share of the spoils, but Naughton had other ideas.
Ballaghaderreen, county champions back in 2008, were the first side to book their place in the quarter-finals with a 1-10 to 1-8 win over Westport. A goal from Mayo skipper Andy Moran proved crucial in the final analysis.
Knockmore were thankful to see a late shot from Aghamore’s Alan Freeman cleared to safety in the dying moments as the North Mayo side qualified for the last eight with an 0-8 to 1-4 win.
Garrymore also got out of their group with a deserved victory over Shrule/Glencorrib while Crossmolina bounced back from their opening round defeat to squeeze out their neighbours, Kiltane, by 2-16 to 3-7.
Cathal Carolan and Paul Duffy got the winners’ goals while former Mayo star Ciaran McDonald landed a string of points.