Neal Hatley has welcomed the return of Mako Vunipola but admits the England loosehead lacks the match fitness to start Sunday's RBS 6 Nations clash with Italy.
Vunipola has been out since December with a knee injury but made his comeback for Saracens against Gloucester on Friday night, lasting 70 minutes.
He will feature in England's matchday squad for Italy's visit to Twickenham, but Joe Marler is set to continue in the starting front row.
"Mako got a few more minutes than was probably expecting against Gloucester, but he did exceptionally well," scrum coach Hatley said.
"He played well and scrummaged well. He carried the ball one hell of a lot for them. That will stand him in good stead."
When asked if Vunipola lacks the match fitness to start, Hatley said: "Yes.
"It's great to have Mako back. To have two looseheads of that quality is a privilege - we have one to start and one to call off the bench.
"Joe has been absolutely outstanding. He scrummaged unbelievably well in the first few games and defensively he's been red hot."
Mako's younger brother Billy has joined up with the squad at their Surrey training base to be medically assessed having been sidelined for three months with knee ligament damage.
"We don't have the results yet and we're hoping that over the next few days we'll have a much clearer picture," Hatley said.
Source: PA
