Jansen (22) packed down at No8 for the Leicester Tigers in their 36-28 loss in the Premiership Rugby Cup to the Newcastle Falcons at Kingston Park, Newcastle.
The rugged loose forward, who had a big season for the Grizzlies then as a loan player for the Old Golds last year, is on a short-term contract with Leicester.
Missing a bunch of regular players, the Tigers named seven debutants, including Jansen, in their starting XV.
Jansen nearly marked his debut with a try but it was waved off when the TMO ruled there had been obstruction in a lineout.
Leicester’s next cup game is against London Irish on March 30.
The Tigers are second in their cup pool, but top the regular premiership with 16 wins from 19 games.
Meanwhile, former Highlanders fullback Josh McKay scored a cracking try for Glasgow in its 30-17 win over Edinburgh in the Scottish derby in the United Rugby Championship.
Glasgow is up to third in the table, behind Irish powerhouses Leinster and Ulster.
