Boli Bolingoli-Mbombo joined Neil Lennon’s Celtic in the summer transfer window.
The former Scotland international striker made an observation about Bolingoli-Mbombo during Celtic’s 2-0 win against CFR Cluj at Celtic Park in Europa League Group E on Thursday evening.
The left-back started the match, and McFadden noted a weakness in the 24-year-old’s game quite early on.
Meanwhile, former Celtic striker Frank McAvennie was impressed with the display produced by 26-year-old defender Christopher Jullien during the first half.
McFadden told BBC Sport: “Bolingoli has a tendency to be on the front foot and to try and nick the ball.
“The Cluj player just lets it roll passed him and it sets up an attack. The Celtic defender needs to know when to try and nick it and when to leave it.”
Bolingoli did not start life at Celtic strongly following his move from Rapid Vienna in the summer transfer window a fee reported by The Scottish Sun to be worth £3 million, but the left-back has been playing well recently.
Against Cluj on Thursday evening, the left-back provided an assist, could have scored himself, and defended well.
Celtic are aiming to win the domestic treble again this season, as well as make an impact in the Europa League.