The Argentine has dazzled for Middlesbrough this season.
The reinvigorated Uruguayan is set to return to the KC Stadium with Middlesbrough on Friday night as both sides square off in a huge Championship clash which could help determine which one of them wins automatic promotion.
He joined Boro in another loan spell in January and things look much more promising for the 25-year-old, who has netted three times in seven Championship outings, and the Hull boss insists he never doubted his quality.
"Unfortunately, we couldn't keep him fit," he said via the Hull Daily Mail. "At times, he did OK and had some really good games – I remember him playing well up at Sunderland.
"But he couldn't get a run of games going to help his fitness levels. He always seemed to nick a hamstring or a calf.
"Certainly, he's had a bit of an impact on them," Bruce said. "He's done well. Undoubtedly, he's got the quality and he's playing at level down from where he was last year. We all know what a good player he is."
City, who have won just one of their last six league games, sit fourth in the Championship table, two points behind second-placed Brighton and Hove Albion, one behind Boro in third.