Based on Pena's lifetime stats, his current binge of HR will even out to about 30 or so this year, while the average will plummet. Fielder could hit 40 HR this year. There are plenty of serviceable MI or 2B players who are having good starts (Hill, Ascrub. Cabrera, etc) who you could plug to fill the avg numbers.
Kemp, Gutierrez, Cruz (DL), Soriano, Bay, Abreu
A.Gonzalez, I. Stewart
Halladay, Marcum, Kuroda, B. Anderson (DL), Leake, I. Kennedy, C. Lewis, Pelfrey, C. Richard, Slowey, B. Wagner, H. Street, O. Dotel, J. Axford.