Matt O'Riley has lifted the lid on Atletico Madrid's bid to sign him from Celtic in January.

The La Liga giants had an initial loan offer with an obligation to buy the 23-year-old for £18m this summer rejected by the Parkhead club during the most recent transfer window.

The Denmark international insists he's 'not upset' that Celtic knocked back the approach for his services, but did admit that it was 'cool'.

He refused to rule out a move away from Glasgow this summer, with the Hoops believed to be seeking £25m.

O'Riley was signed for just £1.5m from MK Dons during Ange Postecoglou's second transfer window, so if he were to move on this summer, the Scottish champions would be in line for a healthy profit.

Speaking to Danish media outlet Tipsbladet, O'Riley spoke of Atletico's interest for the first time.

He said: “Celtic received an offer from them (Atletico Madrid), and that was cool.

"I wasn't really close to leaving because Celtic wanted more money. I'm not upset about it. For me, it was just cool that a club like them would want me. It's not often you receive an offer from Atletico Madrid, so of course, it's great.”

READ MORE: Reo Hatate close to Celtic injury return ahead of Rangers game

On the prospect of the Spanish side reviving their interest, O'Riley left the door open for a summer move. He said: “We have to see what happens.”

The attacking midfielder made his international debut against Northern Ireland in November last year. 

He wasn't initially selected for the upcoming Denmark camp but was eventually called up for this weekend's double-header against Switzerland and the Faroe Islands.

Meanwhile, Reo Hatate has stepped up his recovery from injury by playing some part in a bounce game for Celtic.

The Japanese midfielder took part in 45 minutes of the Hoops' game against St Mirren, which was played behind closed doors on Wednesday afternoon.