When “Taken” returns to NBC this fall, it will look different from the series that premiered last season. Clive Standen will still play Bryan Mills, the ex-Green Beret with the very particular set of skills. But the faces around him will have changed.

Variety learned this week that six cast members will leave “Taken” ahead of season two. The move is part of an effort to creatively retool the drama under new showrunner Greg Plageman. It is also one of several made since May upfront presentations on returning shows. The flurry of changes reflects the effort that broadcasters are willing to exert to sustain returning series at a time when networks are taking a conservative approach to new programming.

On ABC, “Once Upon a Time” and “Quantico” are both undergoing radical casting and creative changes heading into the upcoming season. Both were bubble shows speculated to have been on the chopping block as schedules for next season were being assembled — as were “Taken” and CBS’ “Criminal Minds,” which is also undergoing casting changes.

Casting and showrunner changes are not unheard of in the weeks following upfronts. That span of time, before shooting begins on new episodes for fall, represents the last period in the calendar that creative changes can be made without impacting production. With shooting on most fall series not set to start for another two-three weeks, now is the time for changes to be made.

But the volume of casting changes made in recent weeks is higher than normal — especially the wholesale changes such as the ones at “Quantico” and “Taken,” where the showrunners and most of the supporting casts have been or are being replaced, and at “Once Upon a Time,” where former supporting characters will be stepping into the void left by the departure of former leads Jennifer Morrison and Ginnifer Goodwin.

“Taken” is an international co-production that represents a relatively low cost for NBCUniversal. “Quantico” is an ABC-owned series that performed solidly in its first season but saw its Nielsen live-plus-seven 18-49 demo rating fall 50% in its second season. Both shows perform well internationally, giving the networks that air them in the U.S. (and whose sister studios produce them) added incentive to keep them going — and to hope that creative changes might keep them viable long term.

“Once Upon a Time,” meanwhile, heads into its seventh season. As talent costs tend to balloon late in a show’s life, replacing much of the lead cast could help ABC, which produces the show, keep costs down.

At upfronts in May, broadcast networks displayed patience with even marginally performing current series, renewing many bubble shows and picking up fewer new series in the past.

“The business is clearly changing,” Warner Bros. Television Group president Peter Roth told Variety last month. “It’s a natural instinct to be a little bit more cautious.”

That caution, however, does not mean standing in place creatively on returning series. Programmers are hoping that changes made now can reinvigorate series and keep them on long term.