Arsene Wenger is wary of keeping Danny Welbeck in Arsenal's starting line-up despite his excellent display against Southampton last week.

The 26-year-old marked his first start of the season with two goals and an assists as the Gunners dispatched the home side 5-0 in the FA Cup fourth-round clash at St. Mary's Stadium on Saturday.

Welbeck has battled knee injuries for the majority of the last two seasons and had only managed three brief substitute appearances this term prior to his impressive display against the Saints.

But although he agrees that Welbeck deserves to start Tuesday's Premier League match against Watford, Wenger maintains he does not want to risk a setback for the former Manchester United man.

"He's ready physically to play but we still have to manage the times to use him," the manager told a news conference.

"To come out of what he's gone through, you need to be mentally strong. To play as he did on Saturday is not a gift of God. You have to go through all kinds of suffering to get back to that level of fitness.

"Of course he's done enough to keep his place but at the moment we have to be cautious with him. But the quality of the performance was there."

Arsenal's victory came despite Wenger being banned from the touchline following a spat with the fourth official during the 2-1 win over Burnley on January 22.

Wenger was given a four-match suspension by the Football Association, meaning he will also watch the games against Watford, Chelsea and Hull City from the stands.

"I don't think there's anything to add on that," he said. "I didn't appeal so I accept the sanction and just get on with it and focus on what's in front of me."

Watford completed the loan signing of AC Milan forward M'Baye Niang last week and Wenger has warned Arsenal to be alert against the 22-year-old if he makes his debut on Tuesday.

"I know Niang well because he played for Caen and we had him here [on trial]," Wenger added. "He's a very talented striker individually, and he can create chances.

"He's very strong as well physically, and very quick. I think he will be a major asset for them [Watford].

"He's on loan from AC Milan and we have to keep him quiet because he's a guy who can do something special."