The big German's only start this season has come in the EFL Cup defeat at Exeter, and has otherwise been restricted to four substitute appearances in the Championship, the latest in Saturday's embarrassing 5-0 drubbing at Norwich.
All of which spells bad news for a team over-reliant on the goals of top scorer Scott Hogan, and desperate for someone else to step up and share the goal scoring burden.
Smith said: “He's working hard and he needs to keep doing that to get into the team. Scott's doing what is asked of him, and with us playing just one striker at the moment, it's tough for him or Lasse (Vibe) to get that shirt.
“I just think Scott's a goal scorer first and foremost, and if you play someone up with Scott, they might get in the way of the runs he makes. But it's something we haven't ruled out, and there's been times in training we've looked at playing two up.
“I believe Philipp should be pushing Scotty more, and that's what I've been telling him. We know they're two different players – Scott makes runs in behind whereas Philipp likes it up to feet. We're working on him making more runs into the box so he can score more goals.”