Barcelona's David Villa has been ruled out of Sunday's Primera Division encounter at Malaga through injury.
The Spain striker, who scored twice in the 5-0 midweek Copa del Rey win over Cordoba, picked up a hamstring injury in training on Saturday and has been withdrawn from the squad.
Villa was also forced off in the 77th minute of Thursday's cup tie with a leg injury and Barca say it is too soon to tell how long today's latest setback will keep him on the sidelines.
"The striker noticed discomfort during training this afternoon and, after testing, has been shown to have a hamstring elongation and will not play in Malaga," read a statement on fcbarcelona.es.
"(The injury's) evolution will decide his availability for the next games, as determined by the club's medical services."
Jake Hyde got the show on the road for Barnet with a clever lob over advancing Millers goalkeeper Andy Warrington after 21 minutes, racing on to Mark Byrne's ball down the right flank.
And eight minutes from time Barnet completed the job, Ricky Holmes beating his marker wide on the left and squaring for substitute Andy Yiadom to sweep home an unmissable chance.
Raynor said: "We started brightly and their 'keeper made one or two good saves, but then it petered out.
"We certainly had enough possession, in fact we dominated possession, but we were very disappointed with the result and the performance. Three individual errors were to blame for the first goal, giving the guy an easy chance.
"But with all the possession we had we didn't really create any clear cut opportunities. For the second goal we were throwing men forward and were susceptible on the break, but it was another sloppy goal that could have been avoided and we need to cut those out.
"That's five we have conceded in the last two games and we need to cut those out because it's just not good enough."