The Baggies' boss was delighted with his decision to play the Chelsea loanee from the start after the Ireland international came from the bench to assist the Belgian's winner
Facing his former club, Long put in a masterful performance after coming off the bench and set up teammate Lukaku for the game’s only goal and Clarke revealed his satisfaction at the decision to start the Belgian and bring Long on as a substitute.
"Obviously it paid off, we got the goal," he told Sky Sports. "A super ball from Graham Dorrans who'd just come on to the pitch and a great header down and Rom got the finish that went through somebody's legs.
"The thinking is I have a really good squad. Lukaku has been sitting on the bench for a long time waiting for a start.
"Shane [Long] has been fantastic for me, he's come in, he's done the hard shift, he's always done the shift from the start of the game.
"I actually spoke to him before the game and I said 'It's your turn to have a little rest on the bench and when you come into the game, try and make a contribution' and that is what he did.
"It was a tight game. I think it was quite evenly matched. We probably should've won in terms of chances and shots at goal.
"But we had to be patient, we knew it'd be a tough game, Reading obviously looking for their first win, we came here with a bit more.
"We knew we could win the game but we knew we had to be patient to do it."
The win over Reading propelled the Baggies to third place in the Premier League, just three points behind Chelsea at the top.