"He probably never knew he was going to join Stoke. I thought Liverpool would have kept him and when I heard we were going to get him, I was surprised," Shawcross told British media of the 13 million pound ($16.07 million) signing.
"For the amount of money as well, it's a great signing for the club. He's an even better player than I thought. I've always rated him but I didn't realise he was so good. He's been our best player this season, our catalyst."
Shawcross hoped Allen, who has scored five goals in 16 Premier League games, will be fired up to help Stoke inflict some damage on second-placed Liverpool's title aspirations.
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"He's our main player. Hopefully he can put a good performance in, as the team can. I'm sure he'll be desperate to prove the manager wrong," he added.
Stoke are 11th in the table on 21 points, 16 behind Liverpool after 17 games.
($1 = 0.8092 pounds)
(Reporting by Shravanth Vijayakumar in Bengaluru)
