Celtic have identified a number of potential summer signings as Ronny Deila looks to strengthen his squad.
The manager is looking to fill several positions, and confirmed that the Hearts captain Danny Wilson is one player being considered.
Jason Denayer will return to Manchester City at the end of his loan deal, leaving Celtic short at centre-back.
Deila is, though, keen to re-sign the Belgian on loan, and keep other key members of his team at Celtic Park.
The club's scouting staff have drawn up a list of options for the positions that Deila wants to fill, and an assessment process has now begun.
Deila has a recruitment strategy in place for the summer, which begins with reviewing the performances and development of the players current at the club.
"We have to use April and May to watch players," said the Norwegian. "We need to scout them as much as we can, and talk with them to see if they are the right type for Celtic.
"[Danny Wilson is] one of many names we are talking about, but it's nothing serious in that way. But he's a good player. Central defender is a position we look at, of course.
"Jason is going back to Manchester City to do the pre season. We'll see if we can get him back or not. That's something we want, of course, but we have to co-operate with City.
"Jason is ambitious, he wants to play at the highest level he can. To play is the most important thing, and to play at Manchester City is very hard. If not, Celtic is a good club for him.
"It's about keeping players first, because consistency is everything, then it's to add what we need. We need to pick players who can [make] us better, or young talents who can get to that level."
Denayer's central defensive partner, Virgil van Dijk, would like the Belgian to stay at the club. Denayer made his international debut in the 1-0 win over Cyprus on Tuesday night, and has formed a regular partnership with the Dutchman,
Van Dijk's own future often prompts speculation, and he acknowledges that the lack of coverage of Scottish football in Holland may contribute to him not being called up to the national squad.
However, the defender insisted that at this stage of the season he is only thinking about trying to win the treble with Celtic.
"There was a lot of speculation in the summer that I wanted to leave," Van Dijk said. "Everybody was not so positive around me, but I just enjoy playing here.
"I'm 23, I'm learning every day. I want to get the maximum out of myself, I want to be a better player and a better human being. I close everything when the season is going on, I'm just focused on Celtic. I enjoy every day here.
"Every player wants to develop. Celtic is a very big club and you don't want to leave for a smaller club. We will see what happens in the summer, but as it looks right now I'm still here. I'm not in a rush, but if the opportunity is there, you never know. But I'm just focusing on Celtic.
"I want to write some history here and everybody at the club knows how close we are to getting the treble. That's what everybody wants to do."