Six Nations 2015: Centre Jamie Roberts fears for Wales place

Jamie Roberts (left) and Scott Williams last started a Wales match together against Fiji in November 2014

Wales centre Jamie Roberts says competition for places is so fierce that he fears for his first-team spot.

The Racing Metro player, 28, has been selected alongside Jonathan Davies in the Wales midfield to face England in their Six Nations opener on Friday.

In-form Scarlets centre Scott Williams was left out of the matchday squad, and Roberts believes that is an indication of Wales' strength in depth.

"Your place is always under threat," said Roberts.

"Certainly Scott has had a wonderful season with his club side, and international rugby is about competition for places and it drives me to be a better player."

Head coach Warren Gatland revealed his team to face England on Monday, having originally scheduled the announcement for Wednesday.

Wales have made just two changes from the side that beat South Africa 12-6 in November, recalling British and Irish Lions pair wing George North and hooker Richard Hibbard.

Roberts, who toured with the Lions in 2009 and 2013, will win his 68th Wales cap against England.

Despite his experience and recent excellent form for Racing the former Cardiff Blues player is still wary of losing his starting place.

"You see him [Williams] playing well for his club and you're always worried about your position, you never take it for granted," added Roberts.

"I know this week could be my last game for Wales."