Herrera is one of a number of players who are on the final year of their deals, but the Spaniard hasn't started many games this season.
The Red Devils looked shaky both in their defending and in their passing as Bournemouth looked a threat every time they went forward, with their pace and energy causing a sluggish United side some real problems.
United remain outside of the Premier League's top four but again have a sense of momentum and goal that had eluded them earlier this season, and after his job was reportedly put a risk, the 55-year-old Mourinho told BT Sport: "We were a very, very lucky team".
In Lukaku's absence, Marcus Rashford, who turned 21 on Wednesday, came off the bench to score a stoppage time victor against Bournemouth.
"We were really lucky, because we were really poor". United found the much needed late goal as Paul Pogba lofted the ball from the left flank onto the penalty box which was well controlled by Marcus Rashford who later thumped the ball into the net. I was not at the warm-up but my assistants were telling me this is the best warm-up of our season, everybody very focused with a great intensity.
"The good thing is the team has the face of a fantastic character and the heart that the game is not over and we go until the end".
"Even when we miss chance after chance after chance like we did in the second half they kept going until the end".
But while he admitted that task remains a work in progress, he believes United are showing the powers of recovery required to overcome setbacks and turn games around.
"Same against Newcastle when they were losing, same again at Bournemouth".
Manchester United Chris Smalling has said he and his teammates were "in awe" of Juventus in their recent Champions League clash, and has challenged the players to put things right in their return meeting.
"I wouldn't say it's up", Burley said of Lukaku's United career.