By North-west correspondent Alex Stevens

Liverpool are keeping close tabs on a second Schalke star after tying up a deal for Joel Matip, Football Insider sources understand.

The Merseysiders announced on Monday that they have signed the centre-back from Schalke and he will join in the summer on a free transfer.

Liverpool are also closely monitoring Matip’s team-mate Leroy Sane, who has flourished in a wide attacking role at the Bundesliga club this season.

A source at the Premier League club has told Football Insider that they have sent scouts to watch the 20-year-old regularly this season.

Mane has already been capped by the Germany national team and is regarded as a player of huge potential in his homeland.

The winger has scored six goals for Schalke this season, supplemented by five assists and is on the target list of several Premier League clubs.

Liverpool have already made their first signing of the summer after Matip signed a pre-contract with the Merseysiders.

Football Insider reported on Monday morning that Matip has agreed the terms of a four-year contract worth £60,000-a-week. The deal is worth £12.5million plus bonuses.

Speaking at a media conference on Monday afternoon, Schalke manager Horst Heldt confirmed the departure of the long-serving defender, who is out of contract in the summer.

“Since May last year we have had many intensive discussions, both with Joel and his advisor,” explained Heldt. “It was soon clear that factors we could not influence would be decisive in Joel’s decision.”

Matip, who has 27 caps for his country, explained why he has chosen to leave for Anfield .

He said: “I have always said that I would only leave Schalke for one reason: to get to know something new. I never even considered a move within the Bundesliga.

“Although my decision is definitely not easy, I am convinced that now is the right time to take this step.

“Schalke 04 will remain a big family for me. I was always proud to play for this great club. I will do everything in the next few months to get the most out of this season so I do not feel guilty.”

As revealed by Football Insider in January, the Merseysiders made a contract offer in January to the Cameroon international, who will not cost a transfer fee.

Manager Jurgen Klopp sanctioned a move for Matip, who has come through the ranks at Schalke and is well known to the German from his time in the Bundesliga.