The South African international is nominated alongside Ama Agbeze (Loughborough Lightning), Sara Bayman (Manchester Thunder), Sophia Candappa (Surrey Storm) and Sammy Wallace (Hertfordshire Mavericks) for the coveted award, which is voted for by the public.
Mostert, who has played most of the season at goal-defence, arrived at Team Bath in November following a stellar Netball World Cup where she made the most intercepts of any player.
Director of Netball Jess Thirlby said: “Karla’s addition to the squad has lived up to all our expectations and has actually probably exceeded them.
“We already knew we were gaining a world-class defender but the way she has fitted into our squad and philosophy has been equally as impressive.
“She is very calm and is a massive team player. Her defensive partnership with Eboni Beckford-Chambers has been outstanding from game one against Surrey Storm and that relationship has grown with every match. Add Sam Cook and Claire Brownie to that and we are definitely spoiled in defence.
“Having someone like Karla in the squad is also a massive plus in the way she inspires the younger players. Rubbing shoulders with her in training and working alongside her is undoubtedly helping with their development and that of the franchise moving forward.
“The impact of having internationally experienced players like Karla in our squad cannot be underestimated.
“She has also been very enthusiastic when it comes to contributing to the wider Team Bath Netball programme and in raising the profile of the franchise in the community, visiting schools and clubs to present awards and oversee training sessions. She has a great desire to contribute to the Team Bath legacy.”
Mostert, who plays domestically in South Africa for Bloemfontein-based Free State Crinums, has won 47 caps for her country and played at the Glasgow 2014 Commonwealth Games as well as last year’s World Cup in Australia.
She joined Team Bath along with fellow South African Lenize Potgieter and has helped the Blue and Gold qualify for this season’s Superleague semi-finals.
Team Bath’s own Player of the Season awards are this year taking place alongside the Netball South West Goalden Globes.
The awards dinner will take place on Sunday, May 22 at Somerset County Cricket Club in Taunton and tickets, which include a two-course buffet meal, are priced £25 for adults and £15 for under-16s. They are on sale now in the netball section of the Team Bath Online Store – http://store.bath.ac.uk.