Ipswich Town are said to be interested in a move for versatile Northern Irish defender Cameron Dummigan.
The 23-year-old currently plays for Dundalk in League of Ireland, having started his career at Burnley and then making 83 appearances for Oldham during three loans and a three-year permanent stay.
Teamtalk are reporting the Blues are one of a number of clubs, including Luton, Millwall, Lincoln and Forest Green, to have shown an interest in the defender while Grimsby are said to have had an offer turned down.
Primarily a right-back, Dummigan can play in any position across the back four and has impressed since joining Dundalk in January.
He is due to play in the Champions League on Wednesday when the Lilywhites begin their qualifying campaign against Latvian champions Riga.
The Blues have been linked with a number of versatile defenders this summer, including Dominic Ball, who has signed for QPR after leaving Rotherham.
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Janoi Donacien and Josh Emmanuel are the two right-backs in Paul Lambert's first-team squad, while Luke Chambers and Toto Nsiala are the senior centre-backs ahead of Luke Woolfenden and Corrie Ndaba.
Myles Kenlock is the only specialist left-back, with Tristan Nydam playing in that position during the second half of Saturday's 3-2 loss to Paderborn.
Discussing the Blues' status in the transfer market at the weekend, Lambert said: "I don't get the idea that people think there's money - where's the money coming from?"
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"We can't buy anybody, that's the fact of it, but that's no problem because we have some really good young players.
"They may need a little bit of help but we can't go and buy anybody, regardless of what anyone thinks about deals done before my time and the knock-on of money coming in.
"It doesn't work like that and that's the reality of it, but that's no problem. We've got a good side."
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