Keane is a massive asset - Smalling

The one-time Fulham defender, signed by Sir Alex Ferguson for £10m in 2010, proved the difference at Old Trafford as he netted the fourth and fifth league goals of his career in a 3-1 triumph.

The England international, handed 90 minutes by Roy Hodgson in victory over Scotland in November, opened the scoring within 22 seconds of replacing the injured Phil Jones before adding to his tally on the stroke of half-time at the Theatre of Dreams.

Keane never played alongside the 25-year-old in the senior setup, but replaced him in the 44th minute of a 1-1 draw against Sunderland at the Stadium of Light earlier in the season.

“He’s a massive asset with his age, I think he’s only 22, he was very unfortunate that I think he probably could have seen a future here,” said Smalling.

“But I think he saw an opportunity there to go and play and I’ve seen the last couple of his games and he’s done very well and he’s going to do very well for them. They’ve got a very good catch.

“I think he could be one of the best. For the under 21s he’s there on a regular basis and I think the fact that he’s playing regularly in the Premier League at 22 is a massive sign and a massive confidence booster for himself.

“He left the comforts of United to go to Burnley and to prove himself and he’s well on the way to that.”

Smalling added: “He was very ambitious and it’s paid off, if you back yourself then you get your rewards and he’s showing that.

“I think he can (go on to play for England), a lot of the lads from the under 21s have. When we play with the senior team we watch the under 21s the day before and they’re doing terrifically as well.

“A lot of them now are playing in the Premier League as well, you can see with people like Harry Kane. If you do well in the Premier League then you’re going to be in that senior team sooner rather than later.”

Meanwhile, Smalling also credited the away side’s display and endeavour.

“I think my goal was important because right from the first minute they really pressed us,” he said. “They pressed us non-stop. They were a handful, non-stop runners, and they did make it very difficult.”