The 23-year-old made his first Cherries appearance when he replaced injured Tommy Elphick in the first half of Saturday’s 3-0 win at MK Dons.
Ritchie, whose usual position is on the flank, produced an accomplished performance as part of Cherries’ defence.
The £500,000 signing from Swindon Town had not played as a left-back since being asked to fulfil the role for Portsmouth in August 2010.
Gosport-born Ritchie, a natural left-footer, spent the majority of his impressive spell with Swindon as a right winger.
But with Charlie Daniels sidelined by a foot injury and Elphick hobbling off, he caught the eye by helping Cherries keep a clean sheet at stadium:mk.
Cherries manager Howe said: “He is technically excellent so, with the ball, I have absolutely no worries.
“In fact, he did very well there, technically, going forward. I thought he did excellently and he showed a really good attitude.
“It was not really the debut I wanted to give him, playing in that position. His best position is wide but he did well.
“That was one of the reasons we brought him in – that he can play there. With Charlie out, he did really well for us.”
The former Portsmouth prospect had been a long-time transfer target for Cherries and the Dean Court outfit fended off competition from Championship clubs when they last week sealed Ritchie’s signature on a three-and-a-half-year deal.