Newcastle are the latest team to be keen on the Aston Villa star, along with West Ham, Sunderland and Southampton.
Vlaar, 30, looks set to leave Villa Park at the end of this month, with his deal expiring. He has been offered fresh terms, but with no deal agreed, it looks as if an exit is guaranteed with each passing day.
Eurosport TR claimed that Southampton were leading the race for his signature a couple of weeks ago, whilst it was reported last week by the Daily Star that Sunderland and West Ham have been keeping an eye on his contract status ahead of a potential move for him.
Now Newcastle have entered the race for his signature, as per the Sunderland Echo report, and are waiting to see if he commits his future before submitting a formal approach for him.
The centre-back endured a tough season with Villa in 2014/15, struggling to stay fit and playing just 20 games in the Premier League. He did not impress as he has done before, winning just 0.9 tackles per game, although he did complete two interceptions and 5.8 clearances per game.
He is a proven quality in the top flight, although doubts about last season and his increasing age should make any buying team wary about securing his services.
However, if willing to agree a short-term deal, Newcastle need to sign new centre-backs this summer, and Vlaar would be a good option to strengthen the defence on a short-term basis.