The new Magpies boss hailed the maturity of the Spanish striker in the face of the club's relegation battle.
Tottenham Hotspur go head-to-head with Borussia Dortmund later this week.
West Ham drew 1-1 away at Manchester United in the FA Cup on Sunday.
Ibrox outfit Rangers will take on Old Firm rivals Celtic in the semi-finals of the Scottish Cup next month.
Per Mertesacker says the Gunners must find a killer instinct in front of goal quickly if they are to turn their fortunes around.
Tottenham Hotspur beat Aston Villa 2-0 yesterday, to move to within three points of league leaders Leicester City.
The striker has not played in the Premier League since September.
The 27-year-old has been in form for Queens Park Rangers lately.
West Ham United manage to pick up a 1-1 draw against Manchester United yesterday.
Wolverhampton Wanderers and Birmingham City drew 0-0 at Molineux yesterday.