Reference

Transfer rumors surrounding Shunsuke Nakamura intensified following his successful season with Celtic due to several factors:

1. Performance and Impact: Nakamura was recognized as one of the most technically gifted players in the squad. His impactful performance, especially in set-pieces, significantly contributed to Celtic's success during his tenure. Notably, he clinched the club's 41st league title with a magnificent stoppage-time free-kick, cementing his status as a key player (source).

2. Market Demand: After a standout season, top European clubs were eager to enhance their squads by adding a player of his caliber. The successful season at Celtic highlighted his abilities on a larger stage, attracting interest from clubs like Borussia Moenchengladbach (source).

3. Expiring Contract: Nakamura's contract with Celtic expired at the end of June, allowing him to move on a free transfer. His availability without a transfer fee made him an attractive option for clubs like Espanyol (source).

4. Champions League Exposure: Nakamura's involvement in the Champions League increased his visibility and prestige in Europe, further intensifying rumors and interest from other clubs looking to bolster their ranks for continental competitions (source).

These factors collectively heightened transfer speculations, making Nakamura a hot topic in the football transfer market.