The Bears then made a tactical change, switching from a diamond in midfield to 4-3-3 to get in behind the PSJ back three. This paid off when Simon Lousky got the byline and put an expert cross into the middle for 51-year-old Davidson.
PSJ then looked to attack with more pace and power but failed to breach the defence that was well marshalled by Daniel Kingsley and Oscar Cohen. Harpin did make a save from George Leigh when he went through on goal but that was one of little threat.
The Bears made it 2-0 when Sam Shackleton whipped in a great ball and Davidson tapped in.
Again, PSJ provided a threat the Harpin and his defence, but there is no breach and Shackleton sealed the game with expertly put away shot from a great counter-attack from the inform Bears team.
The last ten minutes of the game saw the Bears keep possession of the ball for the majority of it and they looked in complete control.
Bears joint-player-manager James Harpin told JC Sport: "That second-half performance was probably the best we have played all season. We kept the ball well and when PSJ did attack we soaked it up and countered well.
"They did have a few chances but we kept them out either via a save by me or good defending. The two goals were scored from open play were both quality and it was exactly what we asked the boys to do at half time."
Sam Fresco and Harpin were busy making some late additions to their squad on the eve of the match. Harpin explained: "We had to draft in two new players today - Jack Martin who did excellent at right-back, and Ashley Davidson, who ran his socks off for the boys and got two goals which he fully deserved.
"I've got to nominate several players for the team of the week, we were exceptional as a team. We play PSJ again next week which we are looking forward to. We will have more or less a full squad next week which will hopefully result in a cup quarter-final.
BEARS: James Harpin, Oscar Cohen, Daniel Kingsley, James Levene, Simon Lousky, Jack Martin, Sam Martin, Alex Rose, Harry Russell, Sam Shackleton, Ashley Davidson. Sub: Jack Miller
SCORERS: Davidson 2, Shackleton
PSJ: Joni Hirschowitz, Michael Elia, Daniel Graff, Sam Lavender, Ben Lazarus, Archie Leigh, George Leigh, Gideon Moss, Jack Ottman, Louis Relevy, Alex Rosen. Subs: Josh Cohen, Henry Lewis, Jon Myers, Jake Sandford, Zac Summerfield
MAN-OF-THE-MATCH: Ashley Davidson (Bears)
MATCHDAY 20 REVIEW
