Alan Gaffney admits he is taking a gamble on deploying wing Francisco Leonelli as an emergency outside centre in Saracens' "must win" Premiership clash at London Irish on Saturday.

Regular 13 Kevin Sorrell has suffered a reaction to a troublesome ankle injury that has kept him out of the last four matches. And with tries in short supply Gaffney has switched stand-in centre Rodd Penney back to the wing where he has proved a major threat this season.

That means a shock midfield start for Leonelli, who has experience of the position from test rugby with Argentina.

"It's a bit of a gamble but I didn't quite know what else to do," admitted the director of rugby. "Kameli Ratuvou can also play at 13 but it would require a different defensive structure for him to what he has used with Fiji.

"Francisco has trained particularly well this week and I'm happy with what he has done, particularly in the defensive area of his game. Whether he transfers that to Saturday, we will have to wait and see. He's an integral part of what we're trying to do."

Fly half Glen Jackson is restored to the side after missing the Quins game with a hamstring strain. One other key change in the backs sees the fit again Dan Scarbrough replace Brent Russell at full back for his first senior start since since September.

In the forwards, Cobus Visagie is preferred to Cencus Johnston at tighthead, Hugh Vyvyan partners Chris Jack in the second row, David Seymour comes in for Richard Hill while Ben Skirving reclaims his number eight jersey from Paul Gustard who reverts to blindside flanker.

Saracens: Scarbrough, Haughton, Leonelli, Powell, Penney, Jackson, de Kock (cpt); Lloyd, Ongaro, Visagie, Jack, Vyvyan, Gustard, Seymour, Skirving.

Replacements: Kyriacou, Johnston, Ryder, Chesney, Dickens, Russell, Ratuvou.