While the Lions would have been pleased with their day’s work after bowling the Knights out for 267 in 85 overs, with Kagiso Rabada claiming four wickets, Friend picked up two key scalps with the first two balls of the Lions’ reply.
Stephen Cook was caught at slip off the first ball, and then Temba Bavuma edged the second through to wicketkeeper Tumelo Bodibe to give the Knights an overall advantage.
Rassie van der Dussen and Dominic Hendricks ensured there was no further damage as they saw out the remaining 7.4 overs to take the Lions to stumps on 20 for two.
Bodibe was one of three changes to the Knights side - two of them enforced due to the unavailability of Rilee Rossouw and Pite van Biljon.
Obus Pienaar and Dillon du Preez also came into the team as the Knights lost the toss and were inserted, while Tumi Masekela dropped out.
Aaron Phangiso returned for the Lions along with Brett Pelser as Chris Morris and Devon Conway made way.
Lonwabo Tsotsobe continued to show form and fitness as he makes his way back from surgery, and claimed the first three wickets as the Knights were reduced to 100 for four.
However, Rudi Second dug in - as he did in Bloemfontein on the weekend - as he put on a sturdy 86-run stand with Pienaar, who made 40.
Rabada was the man to break the partnership, trapping Second lbw for 72, and Pienaar fell to Phangiso shortly afterwards to put the Knights in a spot of bother at 208 for six.
It took a plucky 57 from captain Werner Coetsee to lift the Knights to a reasonable score as Rabada found support from Phangiso and Hardus Viljoen.
Coetsee was the last man out when he was bowled by Rabada, who finished with figures of 4 for 57 from 17 overs.
At that stage the Knights total looked a shade on the light side, but Friend ensured that the battle for first-innings honours will be tough on day two.