Roberto De Zerbi listed a number of areas where Mason Greenwood needs to improve after Marseille's 3-2 victory over Union Saint-Gilloise in the Champions League on Tuesday night. The former Manchester United forward scored twice as the French side held off a late comeback from the Belgians, but the fiery Italian manager wasn't entirely happy with his match-winner.Marseille had lost three of their five Champions League games this season prior to Tuesday's outing, making the clash with Union Saint-Gilloise a vital one in their bid to reach the knockout stages. Things started badly as Anan Khalaili struck from distance in the fifth minute, but Igor Paixao replied shortly after before Greenwood got his first of the night njust before half-time. The 24-year-old completed his brace with a superb strike in the second half, finishing from Brighton loanee Matt O'Riley's pass, but Khalaili's second effort ensured a nervy finish for the Ligue 1 side. They held on, however, to earn three much-needed points away from home.Greenwood may have been happy with his performance, but manager De Zerbi insisted more improvement is needed from the former Manchester United striker going forward.The former Brighton manager told reporters: "Yes, I think he's one of the best strikers in Europe. But even he, when we're leading 3-1, needs to learn to manage the ball, not to force things and not to lose possession. And that's not an unreasonable demand, which doesn't mean we're not happy with Greenwood. "He's a great player, but in those moments, I think he also needs to make the effort to hold onto the ball a little longer, to give us a bit more breathing room, to be more consistent defensively, at least by holding his position."Team-mate Pierre-Emile Hojbjerg echoed his manager's thoughts, with the ex-Tottenham and Southampton midfielder adding: "Sometimes, where he can improve is by playing the game until the end. What he does here for us, for the team, is a huge benefit. He's a great guy, and I think he deserves what he's getting. It's good for us."It's not the first time Greenwood has been singled out for criticism by De Zerbi. The Italian raged at the Marseille squad last week after a defeat to Lille, insisting "one shot on target for a player like Greenwood isn't enough for him".Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!It's been a productive season so far for Greenwood. He is the outright leading goalscorer in Ligue 1 with ten strikes, also contributing three assists for his team-mates, while he now has three goals in six Champions League games this campaign. He had endured a lean period prior to Tuesday's win, failing to hit the back of the net in the recent clashes with Newcastle United, Toulouse and Lille, but his midweek showing represented a well-timed return to form. His performances have attracted interest from the Saudi Pro League, with reports claiming a €100 million (£87m/$116m) offer has been put forward for the attacker. If that were to be accepted by Marseille, former club United would be due 50 per cent of the profits.The victory was a crucial one for Marseille, who have been inconsistent during their first proper Champions League campaign since 2022-23. They have lost to Real Madrid, Sporting CP and Atalanta so far but also previously beat Ajax and Newcastle, with this latest result leaving them in a firm mid-table position of 16th. They have two more games left against Liverpool and Club Brugge, with a few more points needed to guarantee the French side a place in the round of 16 playoffs. Back in Ligue 1, Marseille are five points behind current leaders Lens and four off reigning champions Paris Saint-Germain, with their next match coming against Monaco on Sunday evening. A two-game winless run has seen them drop off the pace, having drawn with Toulouse before suffering defeat to Lille.