The 23-year-old came through the Bay system at the same time as international Kane Williamson, making an immediate impact with a century on debut for Bay of Plenty while still at Tauranga Boys' College in 2008.
Since then Popli has set an all-time Bay of Plenty record with six centuries and is just the fifth player to pass 2000 runs for the Bay.
Northern Knights coach James Pamment knows both players well from his time as Bay of Plenty coach and rates them highly.
"Both players have proven they belong at this level and we are very happy with how they have settled into the team and made the step up," he said.
"They both have the right attitude and are capable players with big futures."
The Northern Knights are fresh off their win in the HRV Twenty20 competition on Saturday night in Hamilton and have made four changes for Napier from the last Plunket Shield match in December.
Hamilton's Mitchell Santner returns to the team for the first time since 2011-12 following his stellar recent success in the Northern Districts "A" team programme.
Santner scored 365 runs at an average of 45, as well as taking 12 wickets at 24 with his left arm spinners, at the national "A" team tournament.
Test Black Caps BJ Watling and Ish Sodhi return and pace bowler Anurag Verma is now free from injury.
Wicket keeper Cameron Fletcher makes way for Watling, while Anton Devcich, Jono Boult and Jono Hickey have been omitted.
Corey Anderson, Tim Southee and Kane Williamson are on Black Cap duty against India, while Trent Boult is managing a thigh injury.
It has been a good month for the Northern Knights with many outstanding performances in the "A" team programme adding real depth to the list.
Along with Santner's form and a big century to Popli, James Baker took seven wickets in an innings, Hickey made a double-century, and Brett Hampton has reminded selectors of his talents as an all-rounder.
At the halfway mark of the Plunket Shield the Northern Knights face an uphill, but not insurmountable, challenge to take the second of the three titles on offer. They are currently fifth with 32 points, 30 adrift from ladder leader the Canterbury Wizards.