The Boro manager told reporters: "I'm delighted with Sammy. He scored on his debut and made Scott's goal the other night by beating his man and crossing the ball into the six-yard box. He's had a good impact.
"I think the Championship has been an eye-opener for him. I don't think he's ever been asked to run as hard and as far as he's been asked to run in the last two games.
"But I think it will only help him in the long run and enable him to grow into the Premier League footballer I know he's capable of becoming. We're delighted he's here, and let's hope he can contribute hugely in the next 10 games for us."
Middlesbrough are currently eighth in the Championship table, two points off the playoff places.