Here's Tony Mowbray talking about Jarred and Harwood-Bells prior to the Watford game:
"I know Jarrad has played in the Premier League for Everton but they were never brought here to play together as centre-halves. Ayala, Williams, Lenihan, Wharton - they would all be in the equation, yet here they are and they've been thrown together because of the need to do that.
And they both performed very well.
I thought Jarrad looked like a Premier League centre-half on the pitch, in my opinion, with how fast and assured he was.
They can strike a pass whenever they want too and they're both good players.
It's just not ideal to have two 18-year-old central defenders in your defence in this league where there are wily strikers who have been around the block and they know where to put themselves and how to use their bodies."
Mowbray is an experienced manager and a former centre-half. Sounds ok to me. If he begins to struggle I'm sure he'll leave him out when his experienced players are fit.