JONATHAN Joseph's presence on England's summer tour to South Africa is under threat due to a sprained ankle sustained in Bath's 41-6 Aviva Premiership collapse at Saracens.

Joseph was in obvious discomfort after having the joint on his left leg caught during a tackle by Schalk Burger in the 29th minute and he left the field on crutches.

England play three Tests against the Springboks in June and Eddie Jones faces an anxious wait for an update on the fitness of his first choice outside centre.

"Jonathan looks like he's given his ankle a really good tweak," Bath director of rugby Todd Blackadder said.

"We're not sure how long he'll be out for but he's got next week off anyway. Hopefully it won't be too serious."

Bath leaked six tries at Allianz Park to slump to a fifth defeat in six Premiership outings and contributed to their downfall through wasteful finishing and the mistakes made by their fly-half Rhys Priestland.

"A lot of passes didn't go to hand. Early on I thought the structures were really good. We created a couple of chances but didn't take them and that's been the tale of the tape," Blackadder said.

"We have to nail those opportunities, but instead we gave Saracens three intercept tries and then we were playing catch up. I'm pleased that we still tried to play, but our skill set and execution were poor.

"There were so many missed opportunities and we can only look at ourselves for those. At times we looked a mile away. No look passing and that's three tries."

Three Premiership bosses have been sacked this season and a fourth has left, placing the spotlight over Blackadder's position.

"I can't worry about that (his Bath future). I can only worry about getting the performances we're working hard for. If someone wants to make those decisions, it's nothing I can control," Blackadder said.

"I don't think we're that far away. We just need some extra resources in some key areas. If we get that we'll look a different side."

Saracens' win guarantees them a place in the play-offs and they are one four-point victory away from a home semi-final.

Adding to the positivity that is returning after their European exit to Leinster is the imminent return of their marauding number eight Billy Vunipola from a broken arm.

"Billy is certain for Gloucester, probable for London Irish. We'd like to get him some game time against London Irish, just to get him up and running for the play-offs with a game behind him," director of rugby Mark McCall said.