Mario Been wants more from new loan signing Soren Larsen as Feyenoord bid to avoid the Eredivisie drop this season.
Striker Larsen arrived in Rotterdam on loan from Ligue 1 club Toulouse during last month's transfer window as part of manager Been's plan to strengthen his floundering squad.
The Denmark international made his debut in last weekend's 1-1 draw at Vitesse but failed to impress Been, and the boss wants improvement from the 6ft 4in striker, starting with Saturday's home game against fellow strugglers Heracles Almelo.
Been said: "I put him in in the hope of getting something extra but it did not come.
"With his size I expected Soren to win plenty of duels. I expect more from him but then so does he.
"He lacks rhythm and we will work with him so he can catch up."
Financially-stricken Feyenoord currently sit just one place and two points outside the drop zone in 15th, with speculation mounting they could suffer a surprise relegation this season.