Leeds United boss Marcelo Bielsa was spotted at a League One game over the weekend.
It is claimed that Steve McClaren, the Queens Park Rangers manager, is not put off by Barnsley's £4 million asking price.
Rangers are reportedly looking to bring a new defender to Ibrox.
Rangers are set to see David Bates leave Ibrox this summer.
Leeds United's defence frailties were exposed once again on Friday night, so adding to their options this summer is a must.
Celtic need another centre-back before the end of the transfer window.
Barnsley beat Championship and Yorkshire rivals Leeds United to the signature of Liam Lindsay, who is already being linked with Premier League clubs.
Barnsley pulled off an inspired deal to sign Liam Lindsay from Partick Thistle but the defender is already attracting Premier League interest.
The Barnsley centre-back's dad played as a goalkeeper in Celtic's youth team.
Barnsley held Sheffield Wednesday to a 1-1 draw at Hillsborough in October.