A 25-year-old man who was prosecuted for raping a child last year on Nantucket has been sentenced to serve one year behind bars as part of a plea agreement, a sentence his own lawyer described Tuesday as “unquestionably lenient.’’

Hadi Mohamed Nabulsi, pleaded guilty Monday in Nantucket Superior Court to raping a child and indecent assault and battery on a child under 14, according to the Cape and Islands District Attorney’s office.

Prosecutors said the child was “very young,’’ but declined to specify the child’s age. TheInquirer and Mirror, which first reported Nabulsi’s sentence, identified the victim as a 3-year-old girl.

Nabulsi will serve a year in the Barnstable County Correctional Facility on the charge of indecent assault and battery on a child under 14, followed by five years of probation for child rape, according to court records.

Under the arrangement, Nabulsi would face harsher punishment if he violated the terms of his probation because rape carries a maximum penalty of life in prison, according to the prosecutors and his defense lawyer.

Legal analysts said the plea agreement reflected an agonizing reality in many sexual abuse cases involving young children — the difficulty of securing a conviction without, or even with, the victim’s testimony.

“The circumstances of this case significantly hindered the prosecutor’s ability to obtain a conviction,’’ said James Powderly, an attorney who represented Nabulsi. “Not only would the case be very difficult to prove at trial, the young victim would be forced to further suffer from the emotional harm and trauma that comes from having to testify.’’

Powderly said that while the sentence was far from commensurate with the crime, “all parties involved ultimately decided it was a better option then risking the uncertainties involved with going to trial.’’

Prosecutors declined Tuesday to say how the abuse, which occurred in September 2015, came to light, or how long it lasted, but said there were no witnesses. Nabulsi had no previous criminal record.

First Assistant District Attorney Brian Glenny declined to comment on Nabulsi’s sentence, but said in cases where young children are sexually abused, prosecutors must weigh the difficulties of going to trial, where the child would be required to testify, against finding another resolution.

“We always try to do what’s just and fair, keeping in mind we have young children that are the focus of the prosecution,’’ he said. “They would be the star witness in any trial that would take place. . . . We have to think about what’s going to happen to that child if you force them to go through a situation like that.’’

Randy Chapman, a former prosecutor and past president of the Massachusetts Association of Criminal Defense Lawyers, said plea agreements in child rape cases are often grudging acknowledgments that the charges — however abhorrent — will be difficult to prove.

“Usually when there’s an agreed-upon disposition for the court, it is oftentimes indicative of serious problems with the case, including the ability to prove it,’’ said Chapman, who is not involved in the case. “As a consequence, the feeling is that it is better to obtain some level of justice, recognizing that the alternative may be an acquittal or a dismissal.’’

Larry Hardoon, a former prosecutor who established the child abuse unit at the Middlesex District Attorney’s office, said the prosecution’s endorsement of the sentence suggests the child’s caregiver agreed to the outcome.

“No matter how you look at it, it’s certainly a horrible crime,’’ said Hardoon, who has no affiliation with the case.

Nabulsi had been free on $35,000 bail while the case was pending, court records show.

When Nabulsi is released from jail, he must register as a sex offender, wear a GPS monitoring device, and have no unsupervised contact with children, court records show.

Jetta Bernier, executive director of Massachusetts Citizens for Children, or MassKids, said the case illustrates how abusers are capable of targeting children of all ages.

She said the Enough Abuse Campaign, which was established in Massachusetts and has been adopted in other states, encourages parents to teach children as young as 2 or 3 years old about privacy and ways to keep safe.

One recommendation is to teach children the proper terms for private body parts so they can accurately describe what has happened to them in case of abuse, Bernier said.

“Child sexual abuse can affect infants, toddlers, school-aged children, and teens,’’ she said. “Our mission is to prevent child sexual abuse from ever occurring.’’

Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.