Minutes after their introduction, the Greek left-back had the option of playing it down the line for Milner - but declined and instead came inside with a ball to Takumi Minamino.
The Yorkshireman was quick to voice his displeasure, as the touchline mic picked up his cry of: "Ah Kostas! F*****g hell."
Reacting to the victory afterwards, Milner posted on Instagram: "Wet, boggy... and got caught warmly welcoming Kostas to the team #welcometoliverpool".
Tsimikas replied with "Thanks bro" along with a laughing emoji and a red heart.
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!